Boku benkyou dekinai (or we can't study, something like that), has harem tag, but ends up with 1 girl initially. Then you realize the author made a stroke of genius and made endings for the other girls, which is definitely great, but not a true harem ending. ^^; For Go-tobun no hayanome (quintessential quintuplets), it has harem tag, and while he flirts with all of them, he ends up with one, and this angered most of the readers because it did not feel like she deserved to win, low chemistry and all, low interaction with the MC. Felt hamfisted for an ending.