Bomba!

Bomba! summary:

Tetsu Otani is a junior high school student with a weak heart. Despite the hardships of being so meek at school, he has an intense crush on one of his teachers: Reiko Mizushima. However, one of his least favorite teachers, Kito, intends to propose to her. Since Kito is very violent and often pushes Tetsu around, the thought of him and Reiko together infuriates Tetsu. Before him appears a ghostly white horse, and the next day, Kito is found dead.<br><br>Tetsu realizes that this horse is the ghost of Bomba, a horse Tetsu's father told him he was charged to take care of during the Pacific War. Now, whenever Tetsu feels intense hatred for someone, Bomba will appear and cause that person to die.