The main character is Isamu (Hideaki Machida), a sixth grader . Isamu lost his mother in a car accident when he was young. He couldn't forget that, and he couldn't forgive people who didn't follow traffic rules. Today too, Isamu keeps the yellow flag, a memento of his mother, and makes him guard the traffic lights. He doesn't mind paying attention to adults. Everyone calls Isamu a traffic light idiot , but Isamu doesn't care. It was decided that Isamu would have a new mother. Never admit it! Isamu refuses. But when she learns that her new mother also lost her family in a car accident, she gradually opens up. Eventually, Isamu realized the importance of "caring for the other person's feelings" and realized the mistake in his own way of doing things.