Looks like right away they're acknowledging that he wouldn't last if they started attacking him for sex constantly. Also both Urisugi and Ichikawa struggling to find porn that isn't weird to them. The original h-doujin touched on this early on, but quickly ignored it to show him sleeping around with various girls in different situations... while here, he's realizing that might be too risky, since this is taking itself more seriously than the doujin. So, yes, seems like it's going to be diverging from what happened there. The only parallels are the first proposition moment with Kawashima and when Kanzaki finds out and requests his services. And even around those two events, there were new details and scenes that didn't exist before.
Also, that flashback... makes me think Kawashima is a really good fit for him, even more than I did with the doujin. They both got their perverted start with random porn mags in the woods/bushes. But I suppose they might still push for him being with Ichikawa, even though I feel like she needs a calmer boy like the rest of the males of this world.... but, at the same time, she probably still wants a guy that will take the lead, as she'd expect from her own world, so maybe Urisugi could still work with her. And it's not like he doesn't have his considerate moments, either. He's not just a horny manwhore with this version of him.
And... well, maybe he's just more of a 'heterosexual friends with benefits' type with Kawashima. She probably should find someone more submissive, I suppose, anyway, and rein in her libido more than her mother managed. Or maybe her line ends here because the Kawashimas are just too horny to exist.
And Kanzaki just needs a boy that's just as much of a quickshot as she is. That's it. What, you expect something deeper? So long as she's not feeling like an embarrassment in sex, she should be fine. I dunno what else to say.
Amamiya is fine, she just needs to realize she has to be decisive and settle for one if she actually wants love and not just popularity.