Levia-san, Hii-chan, and Sumida-san try to get Muromi-san to get over her hatred of marine mammals. She hates them because she had a boyfriend in the Mesozoic era who had developed lungs, but decided to stay in the ocean anyway. She thinks whales and dolphins are his descendants. Levia-san tells Muromi-san that that toothed whales returned to sea after having evolved into complete land mammals, which means her ex-boyfriend either evolved into something else or became extinct.

和室见一样用博多腔说话，称呼室见“姐姐”，但和室见不是姐妹的小樋和海豚的关系非常好，然而室见很讨厌鲸鱼和海豚等海中哺乳类，原因是因为中生代时曾甩掉自己的前男友是海豚的祖先。因此小樋试图修复室见和海洋哺乳类的关系，但室见坚绝不肯接受。后从莉薇亚等人中得知自己视水生哺乳动物为眼中钉闹出了大乌龙。从此以后，室见的厌水生哺乳类症演变成了纯粹的找碴

むろみさんの妹･ひいちゃんがやって来た。ひいちゃんは拓朗に、むろみさんがイルカたちと仲良くなれるように協力してほしいと頼む。実はむろみさんはイルカの祖先に振られたトラウマで、水棲哺乳類が大嫌いだった。