Quick speculation, maybe Merize is the author of Hatsukoi Memory, which is based on her own romantic experience with Henri, and she sends the manga somehow to Henri as sort of a letter whenever a new volume release. Though if she could do that, idk why dont she just send a normal letter
Its been a long time since i ever read a manga and just made me go full what the fuck, and I had read Berserk in the past which just felt whatever to me.
Nothing wrong with the author wanting to end their series after they finish telling all the story they want to tell. Always the better option compared to continue stretching on with mediocre plot.