Looking for something like Rakudai kishi no eiyuutan where there's clearly a harem(big or small, doesn't matter), where the MC is pretty much committed to only one girl. Either right off the bat or close to the beginning (Not interested in wimpy mc's that take the entire series to get with one girl in the end.)

Ai Yori Aoshi is this. There are several girls who are crushing on the MC, but he remains committed to the one he is engaged with. No straying whatsoever. It helps that the MC is kinda obvious to the romantic feelings of the other girls.

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Oh, I've finished that one a long time ago. Man it's been a while.

Still not quite what I was looking for, I was thinking more along the lines of horimiya, rakudai kishi and OreDorei.

Completed:
Koibana Onsen
IO somewhat
Mayo Chiki!
Zero no Tsukaima
Shijou Saikyou no Deshi Kenichi
Sore ga Kanojo no Seigi nara think so, but haven't finished it

Ongoing:
Kannagi
Kekkon Yubiwa Monogatari seems that way
Magikano not sure, but seems so
Oda Nobuna no Yabou

Oda nobuna and magikano don't really count, but thanks anyways.

I've read all of the others at some point too

MxO