Anal question 🤔

Hey, so my boyfriend and I have decided to try anal. I'm currently at the stage of exploring on my own before letting him explore before actually doing it. But we were kinda concerned with if in the future it would be okay if he came inside me during it (we're both clean, as we've been tested). If he did, what happens to the cum afterwards? Does it get "pooped" out after or what? Silly question but any answer helps! Thanks!