Tenkuu Island

 (天空アイランド) was the trainee group for Ragdolls from June 9, 2018 until September 5, 2019.

In September 2018, they split into teams Team Clover and Team Heart.

They also had an affiliated group called Tenkuu Island Youth for younger trainees, some of whom were promoted to Tenkuu Island.

Ragken! succeeded Tenkuu Island as Ragdolls' trainee unit.

Final Line-Up

 * Narumi (なるみ) (Founding member)
 * Rune (るね) (Founding member)
 * Sera (せら) (Joined July 2018)
 * Ritsuka (りつか) (Joined August 2018)
 * Miku (みく) (Joined October 2018)
 * Remu (れむ) (Joined December 2018)
 * Manatsu (まなつ) (Joined December 2018)
 * Nono (のの) (Joined February 2019)
 * Akari (あかり) (Joined February 2019)
 * Sara (さら) (Joined April 2019)
 * Nana (なな) (Joined April 2019)
 * Hinata (ひなた) (Joined April 2019)
 * Aika (あいか) (Joined April 2019)
 * Eimi (えいみ) (Joined April 2019)
 * Mashiro (ましろ) (Joined April 2019)
 * Mugi (むぎ) (Joined April 2019)
 * Meari (めあり) (Joined June 2019)

Former Members

 * Arisa (ありさ) (Founding member; promoted to Sengoku Animal Gokuraku Joudo September 2018)
 * Miko (みこ) (Founding member; graduated October 2018)
 * Inori (いのり) (Joined December 2018; left December 2018)
 * Rize (りぜ) (Joined January 2019; left February 2019)
 * Momona (ももな) (Joined February 2019; left February 2019)
 * Karen (かれん) (Founding member; graduated February 2019)
 * Miiro (みいろ) (Joined March 2019; left pre-debut March 2019)
 * Hotaru (ほたる) (Joined July 2018; fired April 2019)
 * Koeda (こえだ) (Joined July 2018; promoted to Ice Cream Cinderella April 2019)
 * Ichigo (いちご) (Founding member; promoted to Ice Cream Cinderella April 2019)
 * Mani (まに) (Joined September 2018; promoted to Ice Cream Cinderella April 2019)
 * Nazuna (なづな) (Joined August 2018; promoted to Ice Cream Cinderella April 2019)
 * Mone (もね) (Joined March 2019; promoted to Ice Cream Cinderella April 2019)