From the following title, Der Anfang einer ewigen Liebe and the summary given after this sentence ends, construct a title in German,with English translations and a summary for a sequel fanfic staying within the them of a crossover of High School DxD, Tsukihime and Fate/Stay Night Prisma Illya, KissxSis set within a crossover world of Code Geass, Majikoi: Love Me Seriously, Zettai Karen Children, Muv-Luv and Eromanga-sensei, with the primary change being Hyoudou Gorou form High School DxD and his wife Miki from High School DxD being the ones to discover Illyasivel von Einzbern when the latter escapes from the Einzbern castle in a mountain district near the Rhine in this fanfic instead of Kirigitsu Emiya from Fate/Stay Night meeting Irisivel when doing buisness for the Einzberns like in canon Fate, thus making Gorou the father of Illya von Einzbern from Fate/Stay Night and Chloe von Einzbern from Fate/Stay Night instead of Kirigisu and Gorou's and Miki's son, Hyoudou Issei from High School DxD be Chloe and Illya's older brother, the fox yokai [monster] princess Kunou from High School DxD being a year younger than both Chloe and Illya and also being Issei's younger full half sister, Ako and Riko from KissxSis in fact being Kohaku and Hisui from Tsukihime, Miki in fact being a member of the Arima side branch of the Tohno clan from Tsukihime, the heiress of the main branch of the Tohno clan, Akiha, Sakura Matou from Fate/Stay Night and Araragi Tsukihi from Bakemonogatari all being the same person, Tsukihi's older twin sister Araragi Karen from Bakemonogatari and Tohsaka Rin from Fate/Stay Night being the same person, Tsukhi and Karen being adopted by Gorou and Miki as their daughters after the death of the head of the main branch of the Tohno clan, Makihisa from Tsukihime with the Hyoudous subsequently moving into the Tohno family mansion from Tsukihime, Kunou and the current heiress of the Arima clan in canon Tsukhime, Arima Miyako, being the same person,  Illya and Sagiri Izumi from Eromanga-sensei being the same person, Akiha and Umezono Hana aka Muramasa Senju from Eromanga-sensei being the same person, Illya and Chloe becoming magical girls like in canon Prisma Illya but having both Rin and Sakura as mentors to help them, which of course backfires when Issei's English teacher who is also his master and the heiress of the Underworld's House of Gremory from High School DxD, Rias Gremory, thinking that Issei had disappeared, pays Issei a visit one night only to see Chloe and Illya being a bit too close to Issei along with the student of Rin's rival Luvia Edelfelt from Fate/Stay Night, Sakatsuki Miyuki from Fate/Stay Night, who is better known as Miyu Edelfelt when Issei catches all three girls sneaking back into the house after killing monsters, causing Issei's harem to grow. One thing to note, Illya replaces Sannomiya Shiho from Zettai Karen Children and has Shiho's powers and abilities in addition to her own, Souna Sriti/Souna Shitori from High School DxD, in addition to being the reincarnation of Ophis from High School DxD replaces  Nogami Aoi and has her powers and abilities in addition to her own and Kuno replaces Akashi Kaoru from Zettai Karen Children in addition to having her powers and abilities in addition to her own, with Illya, Souna and Kunou being this story's version of "the Children" from Zettai Karen Children working under the secret service division of the Japanese Government, BABEL from Zettai Karen Children, which they of course hide from Issei, their parents, relatives and schoolmates: The man who saved Irisiviel von Einzbern from the living hell she was suffering as a vessel of Der Heilige Gral [the Holy Grail] was not a grizzled mercenary disillusioned with the world.

No, this time around it was a businessman [Gorou] and his wife [Miki] visiting the vaterland [Germany] on a business trip [from Japan].

Many years later, Hyoudou Issei learns the truth about his rather unusual family. 

[Author Note Start]A sort of prequel to the hentai manga issue Omodume Box XXVII by Kushikatsu Koumei, which I thought was a rather decent way to close up the Prisma Illya manga and anime spin-off to Fate/Stay Night, despite Omodume Box being of course, a series of doujin where the MC of the mangas chosen for fan work ends up shagging a good number of the girls in whatever series Koumei chooses to cover in the issues. [Author Note end]

The so-called "Ryuu no Oppai" has a near-death encounter that causes him to reevaluate his life experiences and realize how important the closest people in his life are to him.