The claustrophobic and psychedelic sound design of 2000s Japanese games

Hi everyone, I'm doing some research on the sound design of Japanese games from 2000 to 2009. Even in calm scenes, the music often feels claustrophobic and unsettling. It feels like a 'closed-off world' or 'a place you shouldn't see'.

I'm curious how composers achieved this specific atmosphere. For example, Killer7 is 100% insane psychedelic. What techniques (scales, synths, processing) create this feeling of 'forbidden knowledge' or isolation? Does anyone else feel this way about early 2000s Japanese game soundtracks