Kanojo mo Kanojo

Synopsis

The three decide to eat lunch together in the gym storeroom, which has a padlocked door to ensure privacy but an open window they use as an entrance. Saki realizes with Nagisa and Naoya doing cooking and household chores and Naoya doing his best to make both girls equally happy, she is not actually bringing anything to the relationship and fears Naoya will soon prefer Nagisa over her. She becomes determined to do something for Naoya, but with sex not an option, she tries cooking but burns the curry. Desperate to impress Naoya, Saki creeps into his room to try and have sex, but he turns her down. She then becomes upset, believing he prefers Nagisa's larger breasts and returns to her parents' house, which is only next door. Nagisa feels guilty enjoying being alone with Naoya. Naoya tries various ways to apologize and exhausts himself over three sleepless days, but Saki rejects him every time. Still feeling guilty, Nagisa decides to help and tricks Naoya into groping her breast where Saki can see, which causes Saki to rush back in a jealous rage, where Nagisa insists she talk to Naoya.

(Source: Wikipedia)