Hisao tries to skip school by faking an illness, but his mother finds out. Hisao doesn't want to go because he doesn't want to be scolded by his homeroom teacher, Mr. Muramasa, for not being able to do math. The next morning, on his way to school, he is hit by a motorcycle, thinking that if Hisao gets sick or injured, he won't have to go. Muramasa is shocked to hear that Hisao is in such a critical condition that both of his legs will need to be amputated. He learns of Black Jack, who may be able to heal his legs without amputation, and calls him to ask for his help...