The events of both games happen simultaneously, with two different main characters, which is stated in one of the games (I dont remember which one), where Neu mentions the character of the other game. If it was indeed the same person, Neu would recognize him in one of the games, wouldn't she?
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Actually, Neu said in TGRWSMH that Grim Reapers have a bad memory, and forgot almost everything about the mc of that game in only 2 weeks i think. So she may have forgotten how he actually looks like, which would have made the possibility of it being the same character still available, if not for Kamuo confirming otherwise
That is actually quite nice attention to detail on your side, I will agree on that. Although I personally think that the time window was just too short for her to forget, regarding the fact how important the MC is in AGRSS (like... in the history of the reapers), but also how she seemed to remember the MC of TGRWSMH after a few weeks of her not seeing him. At this point however, I want to make clear that it has been quite a long time since I played TGRWSMH, so parts of my information here MAY very ell be wrong. Regarding all of this, I think its quite convenient that the developer themselves confirmed the two protagonists being different people.