A swimsuit thief strikes! But when Rintaro searches for the culprit, he accidentally accuses a legendary dragon: the Dragon of Severe Waves Ren--who is also the Dragon of Storming Jade Rino's older sister! While conducting her own investigation, Keiko is attacked by a mysterious black beast. Now there's a black shadow enveloping the school...! Oh boy, the culprit this time around is seriously tough. This looks like a job for Furuhata...I mean, Rintaro Tachibana!