Basically, what I'm looking for is the MC has a love interest, but that love interest dates someone else. I don't even know why I want to read this, but I do. One of those days. Tough to find too, because simply looking at the netorare tag does nothing as I am not looking for hentai, and lets face it, ntr pops up mostly in hentai.
So yeah. Minor ntr please. I dun wanna jump in too deep at the moment

Lets keep shoujo/josei out of this, unless you really really recommend it. No yaoi either. Yuri's fine.
I would prefer the series completely scanlated, but I'm aware that's cutting the list super short, so it's not a major detail.

My lists are public too.

Thanks in advance~

H2 I guess? The resolution depressed me for days.

Depressed for days? Wonderful. I'll check it out. Thanks~

Spiral - Suiri no Kizuna?
DICE: The Cube that Changes Everything.

Excellent. Added to the wish list~ Shall check them out soon.
Thankies.

I know a few... only I can't remember them... >.>

Maybe:
Shitsuren Chocolatier
Seimaden
Rasetsu no Hana
Cantarella (uh... I don't really remember)

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Kono S o, Mi yo! - Cupid no Itazura-Read the comments, mostly about its NTR, some are spoilers, so beware..
Saitama Chainsaw Shoujo-the female was NTR‘d

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Tournament Round 1
Round 2

Thanks for the recommendations everyone!

Ha, that chainsaw one was nuts XD

I'd also like to add that the webtoon DICE was exactly what I was looking for. So thanks again~

Have you tried the tag Unrequited Love? That sounds like what you're looking for.

If you want the same search with shoujo/josei excluded use http://www.mangaupdates.com/series.html?category=Unrequited+Love& exclude_genre=Josei_Shoujo&perpage=50

(sorry, don't really have any examples)