Koyomi Araragi finds himself alone in Namishiro Park on Mother's Day. Although he tells that he came to the park on purpose, a flashback of his last encounter with his younger sister Karen exposes the real reason behind his short trip to the park. "If you're gonna be like that, Onii-chan—!" That remark left him quite down for a moment... until a familiar voice broke his solitude. Then, with Hitagi just inches from Araragi's face, she tells that after she had paid back Araragi, the two would be friends on equal footing. Friends. That word somehow disappoints Koyomi.