School Days 01x05
Ring of Water
 Makoto and Kotonoha go to the pool for a date on  the same day as Sekai and 6 of her friends. At the pool, it's clear that  Makoto and Kotonoha are dating, however it seems as if Makoto has  developed feelings for Sekai, hinting her that he wants to be with her  instead. Sekai keeps reminding him that he's Kotonoha's boyfriend and  cannot be with her, and tells him to forget about the "practice".