I was looking at the tags for this and noticed while there's no romance/subtle romance/romantic subplot tags, there is a netorare tag. How is that possible? Doesn't netorare come from someone being taken away from their loved one? Could someone spoil to me as to why?

Probably just a blunder or a lot of readers felt there isn't enough romance to tag it romance. Another possibility is the victim is probably completely broken mentally to be considered she actually fell in love with the other guy..

Quote from RS456

Probably just a blunder or a lot of readers felt there isn't enough romance to tag it romance. Another possibility is the victim is probably completely broken mentally to be considered she actually fell in love with the other guy..

But that doesn't necessarily mean netorare.

Can I get a spoiler of the characters it involves?

Nope there is netorare check chapter 142

Quote from dragonil15

Nope there is netorare check chapter 142

I wouldn't consider it NTR, it's just normal Betrayal.

Cap 142 doesn´t feature NTR and i would be shocked if the manga had a scene where the protagonist is forced to watch his lover (willingly) engage in a sexual act with someone else.

The bigger problem is that at least haft the categories are useless or utter rubbish.

I also read EU/US comics and am a librarian.
Manga-Masters, My ANN-Lists + Imdb

Quote from devioustrevor

I wouldn't consider it NTR, it's just normal Betrayal.

Yeah I read that part. It seems like she didn't like either guy and was only doing it to get something.

i would be shocked if the manga had a scene where the protagonist is forced to watch his lover (willingly) engage in a sexual act with someone else

It was a flashback story that began in Chapter 142, but:

his wife intentionally got pregnant with his brother's child in order void their marriage so that she, rather than her husband, would inherit her father's ship

That sort of fits the NTR trope, but she wasn't really "stolen" away from her husband, she engaged in a betrayal to get something she wanted more than her husband. So, to me, it's betrayal, not netorare.