I think the first arc is they're in a school. The mc suddenly got transported in a weird school at night time. (I think? Everything was dark). There was a 'teacher' who's walking around the school to know if they're still students lurking around. He was carrying a dull knife which he use to try to kill the students that he caught.
Gah, I'm pretty sure I've just removed this story from my reading list because it was to gory for me but I couldn't remember the title. Was the plot like this? MC was sucked into nightmare school game/scenario after receiving/giving a bottle of water by a schoolmate. Previously a friend or a friend of a friend of his also disappeared into thin air. So now in nightmare school, MC and others was trying to find the key to leave the school when 1) that schoolmate sort of confessed intentionally dragged MC into the game/scenario as a way of confessing or something before getting killed by the 'teacher' but not before giving 'ability'/'key' willingly to MC 2) MC got killed by crazy dude (probable ML/important side character) with spiked baseball bat in the school infirmary. MC somehow turned back time enough times and somehow cooperated(?) with crazy dude to kill 'teacher' and leave the nightmare/scenario. MC found himself where he was right before he went missing but no schoolmate. Crazy dude was part of organization that went to collect 'key'/'ability' which was needed to be given willingly or kill the holder. Organization wanted to recruit MC (?). Second arc in funfair theme nightmare (?).