Beastman+poly+mpreg+isekai, but for SOME REASON the MC's isekai experience had to start with a sex slavery and SA AND him being de-aged.
Someone uploaded part of the novel for context and it makes me want to drop it entirely, the repeated emphasis on the MC intentionally becoming more like a child as a coping mechanism. Ew...
This is probably never going to be finished anyway, given the update history so I'll just drop it now.
Ai o Ataeru Kemonotachi