Tsugumomo - Vol. 10 Ch. 49 - Red Bowl

[MangaDex]

 

[Wildfire9000]

I'm going to take a guess and say that that black thing is kazuyas sister

 

[superdubes]

I'm going to take a guess and say that that black thing is Kazuya's mom. We saw her using a black obi the night Kiriha "killed" her.