adamstan

Honestly, all they had to do was this. Have it be a year prior to the main story. Have the teacher be a new teacher. During Megumi's sister first month or so he is creeping her out, but she tries to focus on the student council and gets in, along with Megumi. During the next two months it gets worse and eventually he kills her and then goes to jail. Megumi's parents ignore her and the rest of the year is lonely and depressing. Then the next year is when the game takes place. 
But yes, this is a bad route and even with my idea would still make no sense honestly. Maybe it would've been better if he got away with it first and was jailed during the story in the game. But yeah, it's still kind of bad. 
Anyway, I've played this game. Common route is okay and I like the art, but the routes are too short, which would be fine if it had better writing. However, as others as said, since this is drama heavy, it needs a few hours pure route. Doesn't need to be like Clannad, but have some more substance. I do love Hiro and of course Chinastu is okay, but nothing amazing. 
Also, I'm iffy on the developer...He's been shady and you can't buy the game on Steam. It's sad. This game could've been good, even if it was short. 

It seems there's some kind of internal drama within the studio (I'm mostly basing this on gossip, as there was no official communication about this). Steam versions of their games are impossible to buy, but not completely delisted curiously enough (store pages are still up). Versions on other stores are still available. I imagine their latest Kickstarter project, which I even backed, is effectively dead. Kind of sad but kind of fitting too.
And the only thing I'll remember from it long-term is the fact that they just went and had sex in the shower with Megumi covered in blood and a dead body in the hallway... The plotholes become kind of irrelevant by comparison. 

Also, timeline in Megumi's route doesn't compute at all. All those things, that are described like they shoudld have happened over the years, would have to happen over few months or even weeks. Completely illogical.
I think some of the reviewers already pointed it out in detail, but cannot find relevant text right now. However, there's simply no time when all of this
could happen.
It's just physically impossible, especially with 6+3+3 school system. Well, maybe if it was one of those schools that combined both middle- and high- school branches in a single institution, it could be a bit plausible (setting aside the degree to which the school system is or isn't corrupted*), but as it is described in-game now, it's enormous plot hole.
 
*And if anyone wants to see more realistic darker side of VN high-school setting, Aeka's route in Yume Miru Kusuri is the way to go.

Also, timeline in Megumi's route doesn't compute at all. All those things, that are described like they shoudld have happened over the years, would have to happen over few months or even weeks. Completely illogical.
I think some of the reviewers already pointed it out in detail, but cannot find relevant text right now. However, there's simply no time when all of this
could happen.
It's just physically impossible, especially with 6+3+3 school system. Well, maybe if it was one of those schools that combined both middle- and high- school branches in a single institution, it could be a bit plausible (setting aside the degree to which the school system is or isn't corrupted*), but as it is described in-game now, it's enormous plot hole.
 
*And if anyone wants to see more realistic darker side of VN high-school setting, Aeka's route in Yume Miru Kusuri is the way to go.

I'm waiting for the next "Shovelware Adventures" episode then
 

Yeah, if I was writing about Katawa Shoujo I would probably drop the quotation marks. It captured the spirit of JVNs without overdoing it or cynical pandering, sadly can't say that about SSS (although I still don't think it kills the game unless you're really not fond of weeb easthetic).
And right, No One But You! You reminded me what my next VN playthrough to watch on YouTube should be. It's not like me keep skipping on a disaster of these proportions.

Very nice review. Nevertheless, I think I'll skip this VN
You titled your thread on r/vn "Shining Song Starnova - the most "Japanese" EVN ever created [Review]", and after seeing that I obviously immediately thought about Katawa Shoujo. But comparing my impressions of KS and what I read in your review of SSS, it seems that they approach the issue of being "Japanese EVN" very differently. KS managed to fool many people into thinking it was translation of JVN (which is pretty big achievement, I think), and in my memories there are Japanese voices even though it was unvoiced However, it didn't went over the top with "weebness" as SSS apparently does, and it was very good decision (they even presented quite decent in-story justification for dropping honorifics ).
The most obvious example of "over the top weebness and edginess gone wrong" is probably No One But You,  and I'm quite sure that SSS doesn't drop to such horrible levels of atrocity, but while I probably could somewhat enjoy it two years ago (after all, I enjoyed some aspects of NOBY back then), today it would be too much.

I don't think there's any point in arguing about it, it's very much a matter of taste. I found this game too much all over the place - the amount of paedophile executives, psychotic fans and literal shit-eating in the middle kind of didn't let me believe the happy endings. Kamijou was a cool antagonist, but he was an outlier in this regard. It's my personal impression, but that is inevitably the main basis for my review, otherwise it would be dishonest. Same goes for the weebness - some people will find it appealing, some people will get grossed-out Zaka-style and I don't think any of them are "right" about it, enjoyment-wise, but it's still fair to point out how much it is on the extreme end of the spectrum, and that it bothered me from time to time.
I don't fault anyone for loving this game, but for me it did way too many things wrong to be considered great - and it's not just me trying to be an "objective reviewer", they seriously detracted from my enjoyment. It's impressively-made, to the point I kind of feel guilty bashing it, but just OK overall.