Satoyama Katsuki is a carefree 15 year old high school kid, and a pretty lazy one at that. However, he secretly has a crush on a girl who happens to share his name: Mizutani Katsuki. Upon finding out that Mizutani's father used to be a pro-boxer, and she herself infatuated with the sport, he reluctantly joins a boxing gym in order to impress Mizutani. Satoyama is quick to find out he may have the blood of a genius boxer running through his veins...