I know what ntr is but to me this fails to meet the critia, there's no guilt over what she's doing, not even an implied relationship outside the one with the "sugar daddy". in other words its not cheating if there's no one to cheat on....

Base +6, observer1980 +14, backslash -7, RampageSS -9, ChenDosColas +6, Viktorious +4, funsd960 -6

NTR just needs to involve the main protagonist love interest to be taken by someone else. Saber and Rin are in a sexual relationship with someone other than Shiro. Main Protagonist doesn't necessarily have to be dating love interests or even know about the relationship for it to be NTR.

Base +5, observer1980 +14, backslash +7, RampageSS +9, stupid army -9, Popchansky -10

Also, pretty much every MTSP Jin doujins are all NTR.

Base +1, observer1980 +14, backslash +7, stupid army +9

There is a relationship outside you just have to read all series. There is a reason why it is number 5 you know. If it was a stand alone doujin - I wouldagree that this is not NTR but as it comes from the series it is NTR.

Base +15, observer1980 +14, backslash +7, RampageSS +9, stupid army -9, Popchansky -10