Illegal Rare

Rikuo grew up in a house full of yokai, so he always thought they were cool. But the kids in his class talk about yokai like they're bad! When his grandfather announces Rikuo as his chosen heir to run the Nura clan, Rikuo is torn between his human nature and his duties as a yokai. The rest of the clan's not so crazy about a wimpy part-human as their ruler, particularly Gagoze, a high-ranking yokai who would rather eat a human than be ruled by one. (Source: VIZ Media)

The story of the novel series revolves around female middle school student Chiyoko, who is part of her school's naginata club. In her house sleeps a single revolver. That gun is actually able to transform into human form, and in the past, he was created to be an assassin for the imperial city's information bureau. Chiyoko learns of the revolver, whose name is Zerozero Nanashiki (007-shki), and she teams up with him to defeat the halberd tsukumogami Reishiki (0-shiki), who has been killing people for the past few hundred years. (Source: Anime News Network)