"Has an appearance of a young boy, with a mind full of grey matter. He is the great detective, Koikku!"
For the shooting of Gravi and Procella's promotional video, both groups are at a resort island!
From enjoying marine sports to a beach volleyball showdown, both groups are having their fill of the island and summer!
With the shooting going as planned, all that's left now is free time... when a tragic crime has occurred!
Without so much as a single lead on who committed the crime, Koi, claiming the title "the Great Detective Koikku",
has set out to solve this crime!
Will Koikku discover the one and only truth!?
- Kaji Yuki as Shiwasu Kakeru
- Toriumi Kousuke as Mutsuki Hajime
- Masuda Toshiki as Kisaragi Koi
- Maeno Tomoaki as Yayoi Haru
- Hosoya Yoshimasa as Uduki Arata
- KENN as Satsuki Aoi
- Aoi Shouta as Minaduki Rui
- Hatano Wataru as Fuduki Kai
- Kakihara Tetsuya as Haduki You
- Kondo Takashi as Nagatsuki Yoru
- Ono Kensho as Kannaduki Iku
- Kimura Ryouhei as Shimotsuki Shun