My recollection was that Lisa wouldn't talk about exactly was going on. Plus, the only thing that kept it progressing further was the backlash against Eric resulting in his removal from the game. So if he wasn't actually having sex with Lisa at the time, that was where it was headed. It may not yet have gotten to actual sex, but as Eric's stated intent was to fuck Ann and her daughters, that's where it would have ended up. As it was, it was probably blowjobs or something like that for now. Does Max even get to see what's going on during those lessons, or are we just relying on the vague thins Lisa said about it?Just to add to what bacchusplateau says here, nothing sexual happens with Lisa in the event Eric "takes over" her sex-ed.
It's basically the later sex-ed involving Ann & Max "teaching" Lisa, but without Lisa taking part. Also, not NTR. At all.
And maybe not NTR. But if you don't like NTR, Valoryn is correct in that you aren't likely to enjoy Eric giving Lisa sex ed lessons.