I managed to clear difficulty five, but I don't think I'm going to even bother trying out difficulty six. It's a shame that one is singleplayer only, I wonder if it would be doable in a full multiplayer team. It would be fun to try, even if there's no rewards, just to see how it goes.
The worst part was forgetting to download Japanese audio on this PC and having to listen to English Paimon and Keqing and voiceless Yelan.