The only issue is that for some reason...the Yandere never kills the new love interest which is weird since they should (also yeah, Harry should have died at least one time in Aya's hands due to possessiveness).I don't see why you can't NTR a yandere. The target of NTR normally loves the MC anyway. Yandere is just a more crazy form of love. Sure it might be harder to NTR a yandere, but it's fundamentally the same thing.
If anything, you could argue Yanderes are the perfect candidates for an NTR story. The stronger the character's personality and their love for the MC, the bigger the fall.
Would be funny if Luca actually steals Aya and Aya kills him because she thinks he wants to leave her. Mind you. SHE THINKS.
Well, 'play a stupid game, gain a stupid prize' ending. He thought too much about sex and missed the massive life threatening flag the moment blackmail material didn't matter anymore, then again, death/suffering are exciting, would be really fun!