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.
Riddle.
أُحجية
Rätsel.
Acertijo.
Acertijo.
Énigme.
Enigma.
O que é, o que é?
Загадка.