The aunt ntred her nephew. No doubt on that.
You all can say " yeah but the MC cheated on her girfriend first, blablabla " but he is the MC. And because he is the MC, because he is YOU, this law doesn't apply to him.
Yes, it's unfair, but... that's how it works. MC's law.
For example, it's the same with netori and netorare. Netori is good, netorare is bad. The two are the same thing, but... MC's law.
For it not to be NTR, the aunt and the girlfriend have to tell the truth to MC BEFORE any act. AND the MC must be ok with that and gives his blessing to them.
So, NTR tag is needed. Nikki and Haley must die.
The mom, the cop and the maid, best girls.