Kanpai!: v. 1

Yamada Shintaro is a monster guardian - well, a trainee. His job is to protect the monster community from any human harm or from any exorcists trying to kill them. Since he is a trainee, he must vanquish 300 exorcists to be awarded with a temporary license as a monster guardian. Shintaro enrolls in a Japanese middle school. He meets a girl named Nao Arisaka and falls in love with her neckline (unaji). With Shintaro enrolled in school, monsters as well as exorcists now trample the school, and disrupts Nao's peaceful life. One day, a ghost who is obsessed with Nao appears. Shintaro is angry because the ghost is blocking his view of his beloved Nao's neckline. The ghost says he will go to the other realm if his one desire comes true. After many haggling over rituals, a reaper suddenly appears to take the ghost's soul away. Shintaro cannot allow a "death" of a ghost (since ghosts are monsters too) so he tries to save the ghost (by paying the reaper off with money). However, the reaper is suddenly vanquished because an exorcist appears. This new exorcist is Miko Sakurai, and she is in the younger class than Shintaro in the same school.
Miko declares that since Shintaro is the protector of monsters, she deems him as a monster also, and she must vanquish Shintaro eventually. In the next story, the ghost must still have his wish fulfilled. It turns out that all Nao has to do is to say the ghost's name. Nao does just that, and the ghost disappears - only to come back again because he was really only in a coma with a wandering soul. Yabe (the ghost's name) returns to school as a live student and as another "monster" friend to Shintaro. Nao eventually gets fed up with all the chaos Shintaro brought to her because of all the monsters. She explodes, and tells Shintaro never to appear in front of her face again. Shintaro makes a decision to step away from Nao for her protection and happiness. However, as soon as Shintaro draws back, Miko appear in front of Nao and demands to know where Shintaro is. Miko causes chaos to the classroom, and Yabe concludes that they need protection from Shintaro. Meanwhile, Shintaro is in New York, but he already feels lonely from being apart from Nao's neckline. Suddenly, he sees Yabe's "spirit ball" summons Shintaro, and Shintaro believes that something has happened at school.
He quickly returns to Japan, and a fight commences with Miko and Shintaro - with rock paper scissors and acchi-muite-hoi! After a long game, Shintaro loses, and Miko vanquishes Shintaro by punching a hole through his stomach. Shintaro is on the verge of dying, but his desire to live and to see Nao's neckline again awakens Shintaro's dormant power. Shintaro grabs Nao's neck, and bites her! Shintaro seems to be alive again, and a man suddenly appears to help, calling Shintaro "Son."