Malevolent Spirits: Mononogatari Vol. 4 (manga)

It's been two months since Hyoma moved in to the Nagatsuki residence, and he's starting to feel like part of the family. Sure, there's a marriage proposal that both he and Botan are trying to ignore, but overall, things have gone smoothly. As Botan begins her third year of university, Hyoma continues his specialised training.

That is, until a high-level tsukumogami challenges him to a fight. This tsukumogami knew Hyoma's siblings - and also knows the paper umbrella tsukumogami who murdered them. And he knows something else, too - a secret that could shatter Hyoma's peaceful life!