Zaregoto (2002)

an unnamed, cynical college student narrator who gets unwillingly pulled into bizarre, complex mysteries, starting with a locked-room murder on an island of geniuses, exploring themes of genius, meaninglessness, truth, and the struggle to find one's place through philosophical dialogue and intricate plots. Despite trying to remain a detached bystander, he's always at the center, only to find his actions ultimately meaningless, a core theme of nihilism and the search for value in a world of lies and exceptional individuals.