Inside Mari - Vol. 3 Ch. 18

[MangaDex]

 

[gomichandesu]

Idk mate if you're having a period like that you may wanna see a doctor lol.

 

[caocao]

I never thought a period could look that scary.

based Oshimi.

 

[justinx931]

after reading a couple of the author's manga, yes.
he really does make period scary.

 

[FatalVestige]

I have had some periods like this.. they can be pretty debilitating. And it makes sense the male MC would be confused and scared by the pain, nothing can prepare you for PMS cramps.