
You get the shits. Lol. It doesn't necessarily hurt the stomach but causes diarrhea. The semen becomes like an enema. It softens the stool and leads to water stool, diarrhea. In anal sex the anus is usually cleansed via an enema to clear out the large intestine of fecal matter to help avoid that as well as cleanliness but in yaoi manga that is never shown. I know talk of the shits is not sexy at all. Kind of like how the guys should pee after ejaculating because the semen still left in the urethra hardens and then when they urinate, urine stream control is all crazy and all over the place. It is important to pee after intercourse whether you are male for female.
I've been reading many yaoi mangas, yet I still dont know what would happen to uke's stomach if the semen's left inside their ass ??? (⊙…⊙ )
http://www.mangago.zone/read-manga/ten_count/mf/a734cfa84a268cd8dcee778ef170cb85_chapter-12/pg-10/