Kaiyou-bu e Youkoso!

The story is set in the school’s marine activities club. It’s a small club consisting solely of Rena, the senior member, and Haruto. One day, Seto-chan, a prospective new member, turns up and declares that her condition for joining the club is that ‘the two of them don’t get together’. It seems she has feelings for Haruto. But Haruto’s heart belongs to Rena... ?