I think it's because of the monthly ritual, my speculation is like because his scared of Amon and Amon don't want that so like he have a deal with the priest to like clean his memory or something and Amon would like attend or do something the priest wanted
It feels like Amon has been around so long he wants a copy of someone he knew? Thats why he likes him and is getting more protective of MC? Idk just a theory because MC seems way out of sync with him.
idk if i can read this till we find out why and how the mc is having memory loss, it's reminding me of that movie Blink Twice
(if it's already been revealed pls tell me)