Question: When did Kukai travel to China to study?
About the article "Udon", section "Origin".

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Hui-kuo () (746–805) was a Buddhist monk during Tang Dynasty China, particularly in the recently imported Tantric Buddhist tradition from India.
Later, he would become the teacher of Kukai, who in turn founded the Shingon school in Japan.
Hui-Guo was one of two Buddhist masters at Ximing Temple, the other being the Indian monk, Prajñā.
Hui-Guo began his study of Buddhism at age 9, under a senior disciple of Amoghavajra, another Indian monk of the tantric tradition, eventually becoming a direct disciple.
By age 20 (766), Hui-Guo was officially an ordained priest and extensively studied the Womb Realm and Diamond Realm Mandalas, before being fully initiated into the esoteric order that same year by Amoghavajra.
In time, Hui-Guo's prominence attracted students from Korea, Central Asia, and even Java, aside from his Chinese students.
By 805, Hui-Guo was introduced to the Japanese monk Kukai, who writes of the encounter (emphasis added):Hui-Guo began an intensive training of Kukai that finally ended in his death on the fifteenth day of the twelve month (805) by the Chinese calendar.
While the tantric tradition largely died out in China, the lineage survived in Japan through the Shingon school founded later by Kukai. 
One of the adaptations by the Japanese Tendai (Ch.
Tiantai) school was the introduction of esoteric practices (Mikkyo) into Tendai Buddhism, which was later named "Taimitsu" by Ennin.
Eventually, according to Tendai Taimitsu doctrine, the esoteric rituals came to be considered of equal importance with the exoteric teachings of the Lotus Sutra.
Therefore, by chanting mantras, maintaining mudras, or performing certain meditations, one is able to see that the sense experiences are the teachings of Buddha, have faith that one is inherently an enlightened being, and one can attain enlightenment within this very body.
The origins of Taimitsu are found in China, similar to the lineage that Kukai encountered in his visit to China during the Tang Dynasty, and Saicho's disciples were encouraged to study under Kukai. 
The success of the Takaosanji lectures, plus Saicho's association with Wake no Hiroyo soon caught the attention of Emperor Kanmu who consulted with Saichō about propagating his Buddhist teachings further, and to help bridge the traditional rivalry between the Hosso (Yogacara) and Sanron (Madhyamika) schools.
The emperor granted a petition by Saicho to journey to China to further study Tiantai doctrine in China, and bring back more texts.
Saicho was expected to only remain in China for a short time however.
Saicho could read Chinese language, but was unable to speak it at all, thus he was allowed to bring a trusted disciple along named Gishin (義眞) who apparently could communicate.
Gishin would later become one of the head monks of the Tendai order after Saicho.
Saicho was part of the four-ship diplomatic mission to Tang Dynasty China in 803.
The ships were forced to turn back due to heavy winds, where they spent some time at Dazaifu.
During this time, Saicho likely met another passenger named Kukai who was sent to China on a similar mission though he was expected to stay much longer.
When the ships set sail again, two sank during a heavy storm, but Saicho's ship arrived at the port of Ningbo, then known as Mingzhou (), in northern Zhejiang Province in 804.
Shortly after arrival, permission was granted for Saicho and his party to travel to Mount Tiantai and was introduced to the 7th Patriarch of Tiantai Buddhism, named Tao-sui (Dào-suì 道邃) who became his primary teacher during his time in China.
Tao-sui was instrumental in teaching Saicho about Tiantai methods of meditation, Tiantai monastic discipline and orthodox teachings.
Saicho remained under this instruction for approximately 135 days.
Saicho spent the next several months copying various Buddhist works with the intention of bringing them back to Japan later.
While some works existed in Japan already, Saicho felt that they suffered from copyist errors or other defects, and made fresh copies.
Once the task was completed, Saicho and his party returned to Ningbo, but the ship was harbored in Fuzhou at the time, and would not return for 6 weeks.
During this time, Saicho went to Yuezhou (越州, modern-day Shaoxing) and sought out texts and information on esoteric Buddhism.
The Tiantai school originally only utilized "mixed" () ceremonial practices, but overtime esoteric Buddhism took on a greater role.
By the time Saicho was in Japan a number of Tiantai Buddhist centers esoteric training, and both Saicho and Gishin received initiation at a temple in Yuezhou.
However, it's unclear what transmission or transmissions(s) they received.
Some evidence suggests that Saicho did not receive the dual ( transmissions of the Diamond Realm and the Womb Realm.
Instead, it is thought he may have only received the Diamond Realm transmission, but the evidence is not conclusive one way or the other.
Finally, on the tenth day of the fifth month of 805, Saicho and his party returned to Ningbo and after compiling further bibliographies, boarded the ship back for Japan and arrived in Tsushima on the fifth day of the sixth month.
Although Saicho only stayed in China for a total of 8 months, his return was eagerly awaited by the Court in Kyoto. 
  Nadeshiko Fujisaki is a student in the same year as Amu and serves as Queen's Chair of the Guardians.
When Amu rejected the offer to join the Guardians, Nadeshiko tries several tactics to convince Amu to join.
The two become best friends and Nadeshiko looks over and supports Amu in her love life.
However, before Amu and Nadeshiko enter the sixth grade, Nadeshiko leaves Seiyo Elementary to travel to Europe to study dancing.
Nadeshiko is actually a boy named Nagihiko Fujisaki, called "Nagi" as a nickname by Amu and the girls.
It is tradition in the Fujisaki family for males to be raised as females as part of their training so that they may play female roles in Japanese dance.
Nagihiko's secret is known by his family, Tadase, Kukai, Rima (including their Shugo Chara), and the school's principal Tsukasa Amakawa.
Nagihiko has trouble telling Amu that he is actually a boy, instead, he tells Amu that he is Nadeshiko's twin brother.
After Kairi leaves the Guardians, Nagihiko returns and is appointed as the interim Jack's Chair.
She is portrayed by Kanon Fukuda in the musical.
: Temari is Nagihiko's first Guardian Character.
Temari appears to be elegant and Nagihiko's desire to be more mannered and become a Japanese dancer.
However, during Character Change, both Temari and Nagihiko (as Nadeshiko) become aggressive and very masculine; Nagihiko, inadvertently, also gains a naginata, which he promptly uses.
Prior to Nagihiko's return to the guardians, Temari went back into her egg to slumber.
In chapter 34 and episode 98, Temari wakes up after Nagihiko realizes that it doesn't matter what gender a person is, it's effort that they put into something they do.
They perform a Character Transformation, Yamato Maihime, who's attack is 'Robe of Feathers, Dance of the Cherry Blossoms'.
: Rhythm is Nagihiko's second Guardian Character.
Rhythm appears to be cool and outgoing, showing Nagihiko's boy self.
However, he might also be quite a flirt, as is shown when he hugs all of the female guardian chara's after just meeting them.
Rhythm's egg was first seen in chapter 30 and in episode 56, but as of chapter 34 and episode 91, he hatches after Nagihiko remembers how much he liked playing basketball, at his own pace and rhythm, while fighting against a X Character.
During Character Change, huge headphones appear around Nagihiko's neck, and he gains an energetic persona; he also doesn't seem to hesitate in participating in athletic activities, and goes all out dominating several sports such as soccer, baseball, tennis, and judo.
This causes most of the sports clubs to become obsessed with recruiting Nagihiko to their teams, much to his dismay.
When in a Character Transformation, they become Beat Jumper.
Kukai Soma is the upbeat and energetic Jack's Chair of the Guardians.
One year senior to Amu, Kukai helps Amu with her training as the Joker.
Although he was the captain of the soccer club, Kukai loves and excels at all sports.
At the end of the school year, Kukai graduates and goes on to middle school.
However, Kukai returns to visit the Guardians from time to time.
He also becomes good friends with Utau after they go to a ramen eating contest together.
Kukai helps people when they are sad or mad he helps Amu get along with the new Queen and Jack chair and helped her become a stronger character so she does not bottle up her feelings inside.
At the end, he falls in love with Utau.
He is portrayed by Yuuta Koseki in the musical.
: Kukai's Guardian Character is Daichi.
He is very good at sports and cannot seem to sit still.
He was born when Kukai wanted to do many sports but had to choose.
When Daichi and Kukai Character Change, Kukai becomes even more athletic.
When Kukai and Daichi return for a visit, they Character Transform with the power of the Humpty Lock, becoming Sky Jack.
Yaya Yuiki is the childish girl serving as the Ace Chair and is one year junior to Amu.
Yaya often acts immature for her age, such as having an enormous sweet tooth, a great soft spot for items like ribbons, as well as tending to be hyperactive.
She is also a ballerina, though a rather clumsy one.
She has a newborn baby brother named Tsubasa, who, she claims, gets all her parents' attention.
It is because of this that her baby-like Guardian Character, Pepe, was born.
Though she acts jealous around Tsubasa, Yaya does have a responsible side, once personally taking him to the doctor when he had a fever, as no other option was possible.
She is portrayed by Meimi Tamura in the musical.
: Pepe is a baby like Guardian Character who was born from Yaya's desire to remain baby-like in nature.
When either she or Yaya get hurt or something goes wrong, both of them begin to whine and cry in unison.
During Character Transformation, they become Dear Baby.
Rima Mashiro replaces Nadeshiko as the new Queen's Chair.
Although Rima is the same age as Amu, she is petite and has relatively poor athletic ability.
Most of the boys in her class love her and treat her like a real queen because of her beauty and passive personality, while the girls are annoyed by her because of her selfishness.
Because of a kidnapping incident that happened before she transferred to Seiyo Elementary, her parents pick her up after school, but since it interferes with their work schedules, they often argue about who cares more for Rima over work, resulting in Rima often having no one but Kusukusu as company for her secret interest in gag comedy.
Later, she opens up to Amu and becomes friends with her.
When Yaya explains to Rima about Amu and Nadeshiko's friendship, she appears to be jealous.
At first, she is shown to have great dislike for Nagihiko because Amu told Rima and Yaya that he is Nadeshiko's twin brother due to a confusion between the two.
That leads Rima to be protective over Amu and cold toward Nagihiko, although it is implied she is in love with him.
She is a tsundere.
She tells Nagihiko that he is useless because his Guardian Character is still inside an egg, but she gains respect and trust for him later on.
Rima discovers that Nadeshiko and Nagihiko are actually the same person.
She is portrayed by Karen Yagishita in the musical.
: Kusukusu is Rima's Guardian Character and represents Rima's desire to make others laugh.
When she Character Changes, Rima becomes a gag character (which she is embarrassed to use) and uses a signature phrase and pose: "Bala-Balance" (Balancing Balance) from the magazine .
During Character Transformation, Rima becomes Clown Drop.
Kairi Sanjo replaces Kukai as the new Jack's Chair when Kukai leaves for middle school.
Kairi is tall, despite being two years junior to Amu.
Unlike the spontaneous Kukai, Kairi is uptight, very organized, and blunt about faults.
Even with these traits, he is so capable that Amu and Yaya call him "chairman."
Kairi is the younger brother of Yukari Sanjo and was sent to spy on the Guardians.
This was not his choice though, as Yukari immediately begged him to transfer to Seiyo upon discovering that he had a Guardian Character.
Since his sister is busy at work, Kairi takes care of the household work (and his sister) in her apartment.
However, when he saw the true meaning of his "missions," he tries to rebel against Yukari, but not before he reveals his secret to the Guardians when they accidentally discover him with teaser CDs.
He switches sides after Amu convinces him he is a good person.
Afterward, he leaves saying that he promised his parents and local classmates that he would return, but not before declaring his love for Amu, saying that he shall return for her when he has become a man worthy of her.
He also declared a rivalry toward Tadase.
Recently in Chapter 44, he is shown in Amu's town looking for Yukari and comments about also looking for "that person".
In chapter 45, he becomes the adviser for Yuu Nikaido and Yukari Sanjo, who are arguing about getting back together.
In chapter 46, he returns to the academy to meet with Tsukasa, meeting Hikaru and Yaya on his way.
In the final chapter of the manga, it is shown that Kairi and Nagihiko share the same love for old samurai movies.
He is portrayed by Reo Sawada in the musical.
: Kairi's Guardian Character.
Musashi has traits and the personality of that of a samurai.
He also has some of Kairi's traits, such as green hair and glasses.
When he Character Transforms with Kairi, they become Samurai Soul.
Yuu Nikaidou is a former employee member of Easter.
In order to find the "Embryo," he joined Seiyo Elementary and became in charge of Amu's class in the disguise of a clumsy and kind-hearted teacher.
His childhood dream was to become a robot engineer, but when his mentor quit, due to his ailing wife, and his parents opposed the idea, he lost sight of his dream and became a twisted person.
He recovered with help from Amu and Su.
He resigned from Easter Company and officially become the teacher in charge of Amu's class.
A running joke is that he calls Amu Hi"m"amori, meaning "leisure time" much to her dismay.
He dated Yukari Sanjo before the series began, and they broke up.
In chapter 45, they argue about getting back together.
Yukari Sanjo is a former employee of Easter Company, Kairi Sanjo's older sister, and Utau's manager.
She came up with a new project, Black Diamond, to find the "Embryo" and mass-produce X Eggs.
The CDs of the band were freely distributed and the people listening to it had their Eggs removed by force.
As the band became more famous, their song is slated to be released to the Internet together with the unveiling of the band.
She and Utau resigned from Easter after Amu got Diamond back, and started their own music industry called Sanjo Productions.
Yukari once dated Yuu Nikaidou, but the two have since broken up.
She becomes annoyed whenever their former relationship is mentioned.
In chapter 45 of the manga, she and Yuu argue about getting back together.
She is portrayed by Kumiko Kōgami in the musical.
Lulu De Morcerf is an anime-original character in "Shugo Chara!!
Doki—".
She is the new Easter Company worker who has the ability to turn Heart's Eggs into "?"
Eggs and has a hobby of making ruby necklace jewelries which she adorns around her victims.
Her mother is an actress and her father is a French chef.
She wants to find the "Embryo" so her mother will regain her radiance and make acting history.
At first, Lulu dislikes Amu for always purifying the people with Nazo Tama or "?"
Eggs and stopping the "Embryo" from appearing.
However, in episode 63 of "Shugo Chara!!
Doki—", Lulu becomes quite kinder to Amu.
In episode 84, Lulu was fired from Easter.
However, she continued to seek out the "Embryo" on her own.
When Amu finally found out that Lulu is the one who has been corrupting people's dreams, she confronts her in a battle.
Lulu makes many "?"
Eggs, so many that they become two giant "?"
Eggs.
She eventually resorts to making her own Guardian Character, Nana, into a "?"
Egg, and then Character Transforms into Dream Dream.
In the end, Amu convinces Lulu to chase her own dreams and not to force her desires on others.
After her mother lands a movie role in France, Lulu bids farewell to Amu.
: Nana is an anime-original character in "Shugo Chara!!
Doki—".
She represents Lulu's desire to be more carefree and less reserved about herself despite her extravagant upbringing.
During Character Change, Lulu's hair clip becomes a purple flower.
This allows Lulu to use her necklace in order to corrupt Heart's Eggs.
Unlike Lulu's heritage, Nana has a nagoya accent which results with Lulu sometimes speaking in the same dialect, which embarrasses her greatly.
When Lulu used the accent in front of Amu, she complimented it by being cute surprising Lulu.
When Amu and the others find out that she and Lulu are the culprits behind the corruptions of Heart's Eggs, Nana confronts their Guardian Characters to convince them of Lulu's intentions.
Lulu forcebly turns her into a "?"
Egg so that she can Character Transform into Dream Dream and fight against Amu.
She nearly disappeared after she was purified, however, Lulu regretfully apologizes to her and she reappears.
When Lulu's mother lands a film role in France, she decides to move back to France with Lulu.
Rikka is an anime-original character in "Shugo Chara!!!
Dokki Doki".
She is an upbeat, mysterious girl who can understand what X-Eggs are saying, and she can see Guardian Characters even though she lacks a Heart's Egg.
She lives in an apartment room with a bunch of X-Eggs that she collects whenever she sees one.
At the end of episode 2, Rikka becomes a Guardian Apprentice after begging Amu and Nagihiko.
She becomes quick friends with Hikaru.
Later on she finds a yellow egg in her bed with a sun as symbol that eventually hatches into her Guardian Character: Hotaru.
Because she was ignoring the X-Eggs, panic arose when they started shattering.
Saving one of them from shattering triggers her Character Transformation with Hotaru, becoming Pure Feeling.
She then help Amu purify the X-Eggs in her new form.
Rikka is appointed the new Queen's Chair before graduation.
: Hotaru is Rikka's Guardian Character.
Rikka gave birth to her egg in "Shugo Chara!!!
Dokki Doki" episode 15.
She hatched five episodes later.
Before she hatched, Rikka felt lost of herself which subsequently turned her egg into an X-Egg, but it purified very soon.
Hotaru is polite and elegant, balancing out Rikka's energy and spunk.
The two later perform a Character Transformation when her radiance is awakened, becoming Pure Feeling.
Hikaru Ichinomiya is the head of Easter Company.
The people of Easter Company refer to him as "Gozen," although it's revealed that his real name is Hikaru in the much later chapters.
Gozen promised the company employees a successful career if they can present him the "Embryo".
According to the manga, he wishes for a rare one-of-a-kind jewel, thus Easter's search for the "Embryo".
In chapter 40, it is revealed that Gozen is the little boy to whom Amu gave a taiyaki and appeared many other times mysteriously.
This little boy, Hikaru, is unique in that he did not have a Heart's Egg in him like almost all children.
In chapter 41, after his past is revealed, he finally gains one.
It turns out that his egg was actually the shining white egg the others previously suspected as the Embryo.
Hikaru is Kazuomi Hoshina's grandson.
In chapter 45, he receives a Guardian Egg and transfers to Seiyo Elementary, which also happens in episode 103 of the anime and the Guardians make him a Guardian Apprentice.
He is voiced by Shōzō Iizuka when using a voice changer.  
The history of tea in Japan has its earliest known references in a text written by a Buddhist monk in the 9th century.
Tea became a drink of the religious classes in Japan when Japanese priests and envoys sent to China to learn about its culture brought tea to Japan.
The first form of tea brought from China was probably .
Ancient recordings indicate the first batch of tea seeds were brought by a priest named Saicho in 805 and then by another named Kukai in 806.
It became a drink of the royal classes when Emperor Saga, the Japanese emperor, encouraged the growth of tea plants.
Seeds were imported from China, and cultivation in Japan began.