Rakko Umi e Kaeru! Among the world's most powerful otters is Rakko 9-gou, the abandoned and forgotten "Lost Number" who seeks vengeance on the human race. Rakko 11-gou attempts to foil the plans of his adversary, but his "Olivine Tholeiite" attack has no effect on Rakko 11-gou's tail of carbon nanot...

Source: MyAnimeList