Kuro-senpai to Kuroyashiki no Yami ni Mayowanai - Vol. 1 Ch. 10.1 - Extra - Interlude 0

[MangaDex]

 

[Coldlight]

I suppose she was touching his head to let him know Mizuki is close to waking up. It might've been more fun if Mizuki did wake up before he could get his head out of the kotatsu.