Yuuichi lives with his older sisters, Mikoto and Haruna. Though they don't have their parents, they live a peaceful life. Just before summer holiday, Wakaba, his classmate, suddenly says to him, "I love you, please be my boyfriend." Yuuichi likes Wakaba, but... After long consideration, he decides to date her. Wakaba is happy to hear that and soon tells Mikoto and Haruna about it. Yuuichi can see surprise, confusion and sadness on their faces...

Through summer holiday, whom will Yuuichi choose as his girlfriend? Wakaba, Mikoto or Haruna?