Kusuriya, Daisuke

薬屋大助

The main protagonist is believed to be the strongest host in SEPB. His alias is "Cuckoo" (かっこう, Kakkō, lit. Cleridae). Years ago, he shot Shiika's mushi and promised her that he would make her dream come true. However, he does not seem to realize that Shiika was the girl to whom he made the promise. He has a sister named Chiharu, whose whereabouts are currently unknown. His mushi power manifests by powering a gun he carries. It is hinted that the more powerful he makes the bullet, the more his dreams or energy are drained.
Wikipedia