the 4HK and purple-haired girl forgets mc. and in the end, all of the aforementioned people except jiho remember Donnie. i admit, i don't like the ending- i wished all of them regain their memories. but that would undermine the significance of the huge sacrifice that donnie made. even the readers were so frustrated; imagine how disheartened donnie feels. donnie was a coward; she was most scared of her friends forgetting her and throughout the novel/manhwa she periodically had ideas to end their friendship before she gets hurt by these novel characters.
i read a spoiler regarding why they lost their memories. because the original plot had deviated, with reasons idk, chooyoung had to die. donnie chose her friend and saved him, making the original plot's characters have their memories replaced with one where donnie does not exist. i heard Jiho and jooin treated her with suspicion; it's sad since they desperately didn't want to forget her. oh, and donnie realizes she was in love with jiho at this point, but he doesn't believe her... anyway, basically, donnie had a large character development. she fully integrates into the novel, no longer sees her friends as just characters in a novel, and chose her friend over her fear.
with that being said, i don't understand why jiho was the only one to remember? was the depth of ban yeo ryeong's love for donnie less than that of jiho's? what about the ruda, chooyoung, and beo yaodan? the other 4HK?
Inso's Law Webtoon