Ark Academy was chosen as a model case for a school with different races. The teacher came to the academy to give a one-day "assistance" to the idol group "Aquamarine" that the mermaid Erio, who attends the academy, belongs to, but... "I'm sorry, coach. It was supposed to be just for one day..." It turned out that it was a "bus tour that was too happy to go out with active idols from morning till night" on a tour that lasted several days.

Era, a tanned gal idol with big breasts. Ersy, a natural, fluffy idol. And Erio, who desperately clings to him with her slender, frail body.

The teacher, who spends his days immersed in three beautiful idols and sex, is entranced by the mermaid's singing voice and his reason melts away... "A bus tour where you can go out with 3 active mermaid idols from morning till night." Launch okay!? Why is the bus shaking even when it's stopped?