Ark Academy was chosen as a model case for a school that incorporates different races. At the request of Elio, a mermaid student at the academy, a teacher came to provide a one-day "compensated dating" service to her idol group, "Aqua Marina"... "Sorry, Coach. I thought it would only be for one day..." But it turned out to be a multi-day tour, a "super-happy bus tour where you can have sex with active idols from morning till night!" Eira, a tanned gal idol proud of her large breasts. Elsie, a naturally laid-back idol. And Elio, a slender, delicate girl who tries her best to be affectionate. The teacher, spending his days immersed in sex with the three beautiful idols, is seduced by the mermaids' singing voices, and his reason begins to melt away... "A bus tour where you can have sex with three active mermaid idols from morning till night" All aboard!? Why is the bus shaking even when it's stopped?