I Wanted To Interview Japanese Parents

(Please note that links to adult content are included. It makes sense in context.) I would have not thought this was possible if I never heard about this.

The console game industry in Japan allows games based on adult games for their consoles as long as the sexual content is toned down.

I would have assumed these were mostly games with romantic sex scenes or something like that, but I just saw something that blew my mind.

Here, I'll show you.
https://www.amazon.co.jp/エンターグラム-ボクと彼女の研修日誌-通常版-PS4/dp/B07CN3T2NR/
Does the above game look like a game with romantic sex scenes or more like a porn game? Because it looks very porn-like.

And in fact, it is very obviously based on a pornographic series, but CERO rates the PS4 version as being suitable for minors, with a D rating.

Here's the pornographic series I'm talking about. (Adult Links)
https://www.amazon.co.jp/gp/product/B079945GD7/
https://www.amazon.co.jp/ボクと彼女-ナース-の研修日誌-ANIMATION-DVD/dp/B07GZM8ZWM/
You can even see a trailer of "THE ANIMATION" in DMM to see how it has hardcore sex.

Isn't advertising adult games to minors illegal? If so, can you tell me about the law(s) that prohibit this? Are parents in Japan even aware of this?