I just played through the vagrant route and I think people are misunderstanding the game. I like that he set up the game giving you time to remember things - the last week of the previous summer, the bond Keita and Ryoka have and then giving you the option of going to each route on your own. It's not like he could replicate the first game - he's giving every character their after stories after the ending in SoS1. You're seeing Ryoka mostly already corrupted and won over - that's the idea of the game, just expanding onto that pain of Keita now actually seeing and experiencing losing her.
I'd rate the vagrant route a 8/10 or 8.5/10, since it's the only one I played for now. Hot scenes, simple enough premise. Keita lost Ryoka because he simply had no attitude, and didn't show that he cared enough - the dude came in and stole her, body and soul. Tajiri gets her pregnant fast, and they start a family together. The ending with Keita going back to the village six months later and seeing her pregnant - now fully treating Tajiri as her husband, although she did confess to him before that she had a boyfriend - is soul crushing not because of darker things like blackmail or shit of that kind, just inaction. Keita repeatedly reminisces throught the route on how she's the love of his life - but his inability to act made him lose her.
I'll review the others when I play them (I'm going from least favorite characters to favs) but the idea is to show an actual AFTER story. People actually wanted for Ryoka to start from 0 again and are mad because they didn't understand the premise lol. That's why the focus is on the art and the scenes moreso than the "corruption" itself (even though I'm sure Oyama and Yasui will break her even further on this). Welp.