This could have been a clean closure, except for that dumb weakling who was never going to get the girl anyway.
Either the author wants to keep things open for a possible spin-off / sequel, or he just wanted to give this guy some emotional pain just for the sake of it. Anyway, even disregarding his physical state, he shouldn't even be allowed to leave free as Rika described him as a culprit a short while ago.
That might not be enough to condemn him right away, unless Rika manages to get enough of her mind back to bear testimony, but it should be enough to start investigating and monitoring him. There is at least one cop who apparently decided to follow up on her case.
(
Chapter 19, pages 25-28)