Eventually he got caught and the cops charged him with "unlawful abstraction of electricity." Not sure why a simple trespass wasn't applicable, but that always stuck with me.
Was this in Japan? Was he a non-student?
I drove to campus (in the USA) and played MUDs on the terminals all night, and there was nothing to be "caught" for. My friends all did it too. If there were academic restrictions on network use, literally nobody cared. Half of the Network Operations department were gamers and mudders, too.
Well, I'll qualify that, by saying that my friend got in hot water for spinning up long-running game servers on his "personal, recreational" account. We had a special VAX running BSD, dedicated for such accounts. But they still got pissed when we used too many resources.
I just looked up the charge and apparently it was the catch-all crime to prosecute any sort of computer misuse before there were specific statutes.
I think another student ratted him out because there was zero security on the campus back then, except one guy in a hut at the main gate who was probably asleep for his whole shift.
As I understand it he later returned to the campus and shanked another player because they picked up a sword he ejected when he was killed by a fiend, so he probably wasn't liked anyway.