[...] but I've come up to a few things I'm not sure if I haven't triggered another scene or its just something the devs left hanging when they decided to call it completed.
By itself the game is effectively completed, but yes, there's some routes that feel more in hold than finished. But globally it's because they don't really have an end. The MC will not enslave every girls, and secondary characters stories could go on and on for years without really leading somewhere.
Mostly its the playground and subway sections, does the former end with the pet play stuff and the latter the daughter says she'll give you a call after you ask if she has any friends. I could see the daughter on the subways thing totally being something left unfinished.
Hmm, if I remember correctly the two met together near the end. MC present the mother and daughter from the subway to the mothers and daughters from the playground.
But it's all that happen. Many things that could have been added, there were place for dozen of scenes with them. But as I said, all this for what ? It would have added nothing to the game itself, except few more lewd scenes. And there's already tons of that.
The game was about the MC corrupting the city, not about him building a harem with all the girls in the city. So characters like the mothers in the playground, the women in the subway or at church are more to see as a corruption factor. MC stop caring about them, and let them live their life, once they are so corrupted that their sole presence will slowly corrupt other peoples.
By example, all the schoolgirls are now total sluts, in less than one month they'll have corrupted their mothers without need for MC's help. The mothers will then corrupt their coworkers, and so on. All this being made more easy by the fact that here and there, there's few women that are already corrupted.
The only thing that is really missing is probably a global view of the city one year later, with sexual corruption being everywhere. I guess that it would have remove this feeling that some route aren't totally completed.