Touma Inaba, a candidate for the Keio University entrance exam (one of Japan's top three universities), is interrupted when Urara Kasuga, a cute young girl, appears at his hotel room door. She turns out to be his cousin, whom he barely remembers from childhood. Urara, who harbors feelings for him beyond mere cousinly affection, invites Touma to live with her since he has nowhere else to stay. Before the exam, Touma meets Meiko Yotsuba, a beautiful and sophisticated woman also aiming for Keio. Meiko passes the exam, but Touma fails because of a cold contracted from Urara shortly before the test. Despite failing, he pretends to have passed to earn Meiko's respect. Touma finds himself in a love triangle with Urara and Meiko, struggling to maintain Meiko's belief that he is a Keio student while remaining present for Urara.