BL: Fucked up but top-tier plot

Plot is in book's summary but someone is stalking an office worker and leaving his presence in mc's house. Top-tier plot because it was interesting to read at first, the psychological turmoil on mc's part kept me hooked.

SPOILER:
why do they have to fall in love so quickly? Especially the mc?? I hated the way it ended with them living happily ever after. And the other stalker guy wasn't better than mc's stalker just because he was "more mature." He was just as bad.