Kaoru, a friend from the piano class Ruli once attended, has gone missing. While searching for her, Ruli and the gang find a strange dent and her shoes. And as they continue their search, Hiro is suddenly asked a mysterious riddle.
Senpai!
!سينباي
Senpai!
Kiyoshirô !
Senpai!
Vetera!
Старшой!