Alice in Borderland is has the similar set up where a bunch of people are made to fight to survive and are not sure what their purpose is. It's also got a modern vibe, but doesn't have the GARO universe aspects.

Also adaopted from a manga, and about a death/survival game where participants are trying to find out what's behind the game. Gantz is more gorey and features aliens similar to Alice in Borderland's isekai feel.

Both are psychological, with a lot of play around trust, relationships and mystery. In both, they end up trying to figure out what is behind the situation (Alice and the games vs the class and the weird sensei)

Similar setting with "messed up tv show" and psychological theme. Both have a character that manipulates the mc and traps them mentally.