Following their parents' passing, Akito Himenokouji and his twin sister Akiko were taken in by different families. After six years, they find themselves living together, with Akiko harboring a strong affection for her brother. Despite her persistent attempts to create a special bond on their first night alone, Akito remains resolute in keeping their relationship platonic, believing romantic feelings between siblings are out of the question. Nevertheless, Akiko is unwavering in her belief that love knows no boundaries and is determined to challenge her brother's convictions.