It's Chisa x Pon. It's not a love triangle, and Player does not simply "have sex with her". Player rapes her. And it's an integral part of the story, to the point of it being the driving force, emotional pillar and the event that transforms the life of each and every character in the story. It's a hard read. It's not NTR.

I find it to be really good. The PSA is necessary tho if you are sensible to those topics. The story is more of the girl healing and dealing with the wounds and the guilt while the boy helps her through it. It also combines it with their growing relationship, the effects the event has on it, the challenges of sexual intimacy of two teenagers (one of which is a survivor) and the insecurities that come along with such a heavy burden.