From BL-League :

Through his friend’s introduction, friendly and cheerful Nishino became roommates with Maki, his kouhai in university. Living with the unsociable Maki, whose personality is the opposite of his, makes him feel troubled all the time. But after realizing Maki’s kindness and consideration, he gradually felt comfortable being with him. However, at that moment Maki told him “I like senpai, so I can’t stay with you anymore”. He can’t respond to his feelings but he wants to be with him. Nishino flatly rejected Maki’s confession by saying “It’s just your delusion” and continued living with him but... Cohabiting life between a cool kouhai and an airhead senpai! A newly drawn story included!