Question: Chou Tzu-yu is part of the girl group who debuted on October 20, 2015 with what EP?

Context articles: Twice discography
Lee Hae-in (singer)
Black Pearl (K-Pop Group)
Chou Tzu-yu
Youth Society (S.H.E album)
Little Mix discography
Twice (band)
Nandome no Aozora ka?
Twicecoaster: Lane 1
Like Ooh-Ahh

South Korea-based girl group Twice have released four extended plays (one of which was reissued under a different title), one compilation album, one compilation EP, and five singles.
 Formed by JYP Entertainment in 2015 through the survival show "Sixteen", Twice debuted in October 2015 with the release of their first EP, "The Story Begins", and its single "Like Ooh-Ahh".
 The EP and the single peaked at No. 3 and No. 10 on the Gaon Music Chart, respectively.
 "The Story Begins" eventually sold over 120,000 copies, becoming the best-selling debut extended play by a K-pop girl group of all time, breaking the record set by Girls' Generation's first extended play "Gee" (2009), which sold nearly 100,000 copies.
Lee Hae-in (born July 4, 1994) is a South Korean singer and actress.
 She debuted in project girl group I.B.I, a project girl group that consists of Produce 101 eliminated contestants formed by LOEN Entertainment, which debuted in August 2016.
 In 2017, she joined another survival girl group show, Idol School as a contestant.
Black Pearl (Hangul: 블랙펄) was a South Korean girl group official made up of Oh Nami, Hwl Eun, Young Joo, and Mikka.
 When the group debuted in 2007 they marketed as the new girl group to dominate the girl group charts in the following years of 2007 and 2008 alongside some artist Wonder Girls, and Kara.
 They were also known to follow the steps of SG Wannabe, SeeYa, and M2M.
 In 2009 Mikka left due to personal reasons.
 New member Jung Min was added by 2010 or 2011.
 As for the 2010 and therefore the group only consisted of the following 4 until their disbandment in 2012.
Chou Tzu-yu (born June 14, 1999), known as Tzuyu, is a Taiwanese singer based in South Korea and a member of the K-pop girl group Twice, under JYP Entertainment.
Youth Society () is the second studio album by Taiwanese Mandopop girl group S.H.E.
 The album was released on January 29, 2002 by HIM International Music, four months after the group's debut album, "Girl's Dorm".
 It features S.H.E's first collaboration with Jay Chou, who composed "熱帶雨林" (Tropical Rain Forest).
 The song would later be performed live with Chou during the first five stops of S.H.E's Perfect 3 Tour.
 This album features a larger number of covers relative to "Girl's Dorm", including "Remember", "給我多一點" (Give Me More), "催眠術" (Hypnotism), and "I've Never Been To Me."
The discography of British girl group Little Mix consists of four studio albums, seventeen singles and eighteen music videos. Having become the first ever group to win the show, winners of "The X Factor" Little Mix released their debut single "Cannonball" a cover of Damien Rice's single in December 2011.
 The single became the group's first number-one single when it topped the UK Singles Chart.
 The lead single from their debut album "Wings" became their second number one single in the UK.
 It also reached number three in Australia and number 14 in the New Zealand.
 In November 2012, Little Mix released their debut album "DNA".
 The album peaked inside the top 10 in ten countries, including the UK where it debuted number three.
 The album has been certified Platinum in the UK where it has sold 391,447 copies there as of April 2016.
 In May 2013, the group released their debut album in the United States, where it debuted at number four, becoming the highest debut from a British girl group in the US, beating a record previously held by the Spice Girls, who debuted at number six with their debut album "Spice" in 1996.
 "DNA" spawned three more singles; the top three hit and title track "DNA" and the top 20 singles "Change Your Life" and "How Ya Doin'?
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Twice (; Japanese: トゥワイス) is a South Korean girl group formed by JYP Entertainment through the 2015 reality show "Sixteen".
 The group is composed of nine members: Nayeon, Jeongyeon, Momo, Sana, Jihyo, Mina, Dahyun, Chaeyoung, and Tzuyu.
 The group debuted on October 20, 2015 with the extended play (EP) "The Story Begins".
"Nandome no Aozora ka?"
 (何度目の青空か? )
 is the 10th single by Japanese idol girl group Nogizaka46.
 It was released on October 8, 2014.
 It debuted in number one on the weekly Oricon Singles Chart and, as of October 20, 2014 (issue date), has sold 478,888 copies.
 It also reached number one on the Billboard Japan Hot 100.
 It was the 8th best-selling single of the year in Japan, with 578,174 copies.
Twicecoaster: Lane 1 (stylized as TWICEcoaster : LANE 1) is the third extended play (EP) by South Korean girl group Twice.
 The EP was released digitally and physically on October 24, 2016 by JYP Entertainment and distributed by KT Music.
 It contains seven tracks, including the lead single "TT" (refers to the emoticon used to express crying or sadness).
 The EP is the highest selling K-pop girl group album of 2016, which sold 350,852 units at year-end.
"Like Ooh-Ahh" () is a song recorded by South Korean girl group Twice, the lead single of their debut extended play (EP) "The Story Begins".
 It was released on October 20, 2015 by JYP Entertainment and distributed by KT Music.
 It is written and composed by Black Eyed Pilseung and Sam Lewis.