Risa Amakawa is only in high school, but she is extraordinarily self-sufficient. With the tools inside her seemingly bottomless bag, she is prepared for any freak incident that lady luck chooses to throw her way. So when Risa encounters a delinquent—all battered and bruised—on a rainy afternoon, she takes advantage of the power bestowed upon her by her own sense of caution and uses it to help him. What she does not expect is the victim, Zen Oohira, to take a liking to her.

Zen checks all the boxes of a typical delinquent; he has an air of nonchalance about him and even owns a motorcycle. Even so, he is oddly cheerful and sweet, going so far as to give Risa a "help coupon" as thanks for her aid in his time of need. When an unforeseen episode forces Risa to redeem her coupon, she realizes that Zen can be far more charming than he lets on. But is she prepared to sacrifice her meticulousness for a carefree gamble on romance?