Actually, if I followed correctly, this guy is the type to try to help people and also to not take any shit coming from a group of grunt. So he beated one grunt ass in the vol1 and if we follow correctly this one, they setted up a trap so they could get revenge on him. Except if the plot give us a twist, they certainly beated him to death, breaking his legs and arm, making it obligatory to amputate his members. And this girl actually cheered him up.
Now, based on volume 2 & 3, here is where a translation could really help: Did she chose to keep him because she always loved to keep broken animals when she was young? Did she set-up the whole story so she could keep him? Did she plan to help him and then things get really twisted for them?
In volume 2, we can see that he got rape by the guys but in it, he seem to be already amputed. So here is the thing: Either he got his member broke and cut by the guys who kidnapped/beat him to death and he was raped. Or (and this is REALLY worse), she made him rape by other guys...
Also, based on volume 1, the girl he actually helped one night apparently killed herself (or did a bad thing to herself) after they had a fight.