I still don't know what's the exact meaning of the genre angst, but this manhwa has themes of psychology, morality and emotional/complicated relationships, so I'm pretty sure it's close, lol. MC and ML match each other's freak. In the way that neither of them are green flags, but they're very compatible for each other. I think I'll give them both yellow flags, they aren't terrible people, but they might have anxiety, depression and a bunch of unresolved trauma, which actually keeps the plot interesting. Like the name goes, it feels like a game of chess between former rivals. Totally recommend.