"When I'm in the water, I'm not sure whether I'm crying or not."
Rio belongs to the swimming club and is an excellent swimmer. She has even been told by the club adviser to help out Yokoyama, a member who can't swim, because she's good at teaching others how to swim. She is also a close friend to Jun, another swimming club member. What will happen to these three?
The main story consists of three chapters while the volume itself contains two one shots.