As a separate game, Scars of Summer After really isn’t NTR at all. There’s no corruption, stealing, or debauchery that the first game hadn’t already developed. In fact, some of the early scenes (like Nobuo’s first few scenes) kind of felt like SAO II, where they kind of reverted the existing progression to just add scenes that were teasing back into sex. Since she already fell in the first game, diving back into it just felt like watching sex scenes between lovers (the most NTR thing is that they’re just ugly/cliche NTR tropes).
There was a lot of hype since it’s been around 4 years, but I guess it technically is just an after story/additional CGs for a story that already finished. More animations and CGs were nice, but I was also slightly disappointed and couldn’t really enjoy it in terms of NTR either.