Uwah I also saw this on booktok
Uhm this two are not like worst enemy but both mc and ml have an amnesia. They also both latches on to one person
https://www.mangago.me/read-manga/false_memories_lee_gpiee/
https://www.mangago.me/read-manga/mr_fiction/
But this one is I think have some of the criteria for the 'worst enemy' since he make the mc latches on to him and the mc not knowing that the ml is the one who made him hospitalized that made him have an amnesia.
https://www.mangago.me/read-manga/i_don_t_remember_that/
okay i saw this on booktok and really want to read similar troupe… copy paste- the mc gets amnesia and latches onto one person."I don't remember you but I get the feeling we used to be close? but it's their worst enemy. "Oh, absolutely"
(any straight/BL/GL is okay)