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Taichi is a fat teenager and a horrible embarrassment to his little sister, Mika. She saves her own image by refusing to acknowledge him in public, but that won't work forever. In order to solve the problem, she enrolls him at a boxing gym, hoping the exercise will make him lose weight. At first, Taichi is very hesitant about the whole idea. Soon, though, his trainer Kurata's tough encouragement makes him feel like he might actually be able to become good at this sort of thing. But while the boxers at the gym accept him as a fattie coming in to jump rope and hit punching bags, will he be able to get them to accept him as a boxer-in-training? And does he have what it takes to become an actual boxer?
Ando Hanaka wanted to become stronger because she thought she couldn't protect her friend from bullies. Now as she enters high school, she seeks to enter many of the martial arts clubs in her school. Unfortunately for her, many of the clubs reject her due to her frail and small size. She just wants to be stronger, but is it going to be impossible for her?
Goshima is a boxer who has held the world championship title for years and never once lost a match - thus earning himself the nickname 'Zero'. His coach, Araki, describes him as 'a flower that blooms only within the ring'. But with his 30th birthday approaching, everyone begins to question Goshima's worth. Thus he decides to look for the ultimate opponent to give him his final match.