Can someone translate this? It might help to see why it's soul-crushingly depressing. :/

I'd expect it's depressing because that girl is missing her body past the torso.

And he likes her legs, or something.

The text is spoken in Rika's style, and reassures Keiichi that he isn't responsible for what happened.

This looks like it may reference a scene at the end of tatarigoroshi-hen, where Keiichi thinks he has killed various people by wishing them dead. He didn't do so in Rika's case, but still seemed to blame himself when he finds her messily eviscerated. Oh, and with crows present too, as if it wasn't already bad enough.

I suppose this post may be in this pool due to how he would feel; finding the corpse of a friend, and believing oneself to be somehow the cause, can't be pleasant. Rika's inability to comfort him perhaps also plays a part...