You mentioned the family was in Japan a few posts back, so I got confused. For a moment, I thought you were saying the whole thing was in Japan this time since it's only a few towns over.
Having other males around can work as long as they are limited and done well, but in some ways it's like a voiced PC in an RPG, not only does it limit your RP ability by forcing a personality on you, but every bit of resources that go into doing it is time/effort/money that could have been spent on something sexier. Personally, I always groan when I have to interact with the 'best friend' character or whatever, and skip through it as fast as I can, just eager to get through the scene and on to something fun. Like with the Voiced PC example, not only do they take away from the 'fun' parts of the story, but I have to worry about them wanting to get with 'my' girls.
Back to Milfy, while I like the dad, as I implied before, he has become an impediment to screwing the twins. The Headmaster was just introduced, and while I like him, he is already getting blown by a hot girl I want to myself... Hell, even your last rewrite here with Des, letting Tuck have her for so long made me a bit uncomfortable, not that I am complaining. I agree, at the end of the day, you have to be happy with what you are working on, and I would never presume to tall you what to do, I only make suggestions as they come to mind. Ignore what you don't agree with, I am a far cry from perfect or an expert, when brainstorming, I don't even like all of my ideas, but as I always say, 'even a bad idea, can inspire a good one'.
One more suggestion for the moment, don't do the intro as a long exposition, this is true for any story, be it a game, book, movie, or whatever. If you have to have it be long, make it interactive and break it up a bit, have people talk, make jokes, move around some, that sort of thing, give choices if at all possible. Remember the old adage, 'show, don't tell'. Even if it's skipable, no one wants to read an essay before they start a porn game. Try to keep the explanations short and to the point. You can have more detailed info in a help menu, or tooltips or something, if you feel they are warranted.
Remember, STS is more of an adventure game, than a normal visual novel, so you want to allow more interaction than just reading. That said, you also need a balance between the text being too long, and too short, having to click for every word or two is a pet peeve of mine anyway...
For a Japanese character, it could be fun to break a lot of stereotypes, like a cross between Eve from STS and the Asian girl from Big Hero 6. She could be loud, affectionate, likes hard rock, not modest, and so on. Here is a suggestion, that is if you do have them/him having lived in Japan at some point, maybe they met while he was there (even if just visiting), and they became friends, but stayed in touch on-line. So, when he starts working on the project, she can help some at first thought e-mails, then eventually he could pay her for some contract work, and eventually it takes off enough that she moves to his town to be better situation to help (and many they flirted a bit over the years and she is a bit interested), this sort of thing works better if you go with the idea that he has made a number of games by the end of the story, having started by himself making one small game that didn't do too well, to running a small studio several games later. We can learn more from our mistakes than our successes after all.
Yeah, it doesn't really matter what his game(s) is(are) about, the inception thing was just something that was making me laugh. One idea is to have his games be parodies of ones you think are at the right level, starting with something that either is very simple, like Akabur's Mating Season or Magic Shop, or worse, something that gates completely abandoned, maybe even those are two possible endings for his first game, depending on the choices made...? Even a failure, where you made some design choice that dooms the project like including a kink that too many of your core supporters hate, some troll starts a smear campaign, or some other random thing that ruins everything. It would be an interesting way to go, neither being a bad end for your game, even if his failed, but it sets him on a slightly different path, and while you might still get to the same place in the end (super awesome game maker), the story changes slightly depending on how each of his projects goes. Each one of the games he makes could be a different chapter in his life, and the game, not to mention it gives you a good reason to spread out introducing new characters as you go, as he will need t expand and talk to ore people for each new game.
