With the tail of her ghost half tucked between her legs and her gently caressing it I'd say this mastubation. I'll wait for a second opinion before adding tags in case I'm just being huge pervert and looking at Youmu with lewd eyes again.

Monki said:

With the tail of her ghost half tucked between her legs and her gently caressing it I'd say this mastubation. I'll wait for a second opinion before adding tags in case I'm just being huge pervert and looking at Youmu with lewd eyes again.

From Twitter

ｽﾔｧ

She is just sleeping, no lewdness going on here, Monki boy.

Randeel said:

She is just sleeping, no lewdness going on here, Monki boy.

Does look very suggestive though, which was probably the artist's intent.