You're awesome. I think we're all curious!

I also appreciate this!

I wager it's one of the most dense and plot heavy installments. Plus the twins expansion sheds light on their backstories, and the whole White Cat Brigade sidestory is like another game itself, though that and the Ai/Aki (the redhead sisters) stuff is what's sadly left unfinished.

It turns out that Goku is incredibly dense! I'm also recording everything in a google doc (a nasty transcript/summary hybrid) with some notes, so its taking even longer. It turns out that I forgot just how much happens in this one. I apologize for how long this may take.

My first real "update" will be after I clear the first main route (bad ends included)

Yep, you're officially going to be one of the fandom's heroes for that. Thank you so much!

I guess you could say you will be VeryImportant now.

I suppose for the time being I can read the translation of the Inyouchuu Kyou light novel
I know from looking at the art for it that Rinko is included, unlike how Kikua and Ouka were excised from the Shoku light novel

Also, I recently re-watched the original Inyouchuu OVAs, and I hadn't realized before playing the remake of the first game how the plot was just non-existant in the adaptation.
It's just "Sui gets rescued at night by Mikoto, they're joined by Yamato to check the school's pool, tentacles appear and all of them are dragged into Nightmare's bio-cave where the girls are tentacle raped and Yamato is NTR'd so hard he melts into a pile of goo"
Takeru doesn't even exist!
While I'm sure the Shoku and Etsu OVAs also leave lots of the games out, at least they have a premise they set up first before the bad end routes begin.

Right? Honestly, what I remembered about the OVA sort of affected my expectations about what was going to happen in the remake. In the sense of "Oh, wait, they're in the pool room at night... any moment now we'll have to make a choice that'll keep Mikoto from getting captured!" ... and that never actually happened. Though I would note that the context it does give us seems to imply that Sui was sitting in the hallway intentionally to bait the monster, already working together with the Black Cats to try and take it down. Example being her apologizing for being "too slow."

And yes, the lack of Takeru in a story that hinges entirely upon Takeru is a pretty significant oversight!