Goushi Hirose, a third-year student, loves his younger sister Noa a bit too much, to the point of keeping her photos and pillows. Hoping to suppress his feelings for her sake, he moves to Tokyo to get away. He lives alone, yet he fantasizes about his sister every single day. Three years later, his sister calls him. She tells him that she will be taking an entrance exam at Myouzen University, a school close to his. Noa passes her entrance exams, marking the beginning of the siblings' life in the one-room apartment together. Little does Goushi know, Noa also loves him, possibly in an even more ridiculous manner than himself! She will do anything to make her brother submit to her while striving to keep rivals and threats to their love at bay.