Weren't the storylines for the routes already revealed? You kinda already nutshelled them pretty good. Terena's spell gets reversed on her and she's blackmailed by the Shota into sex because he recorded the session where she was stupid and begging for his cock in the skimpy bikini... Rietta is hypnotized by the priest with that circlet and gets corrupted... and Arika enters a contract where she has to serve Lord Boner and she gets hornier and hornier until she willingly decides to become Boner's cocksleeve.
Nothing Takeda hasn't already done in some form or another in his doujins... only this time we have full colored CG, sexy outfits like Terena's cow costume and Arika's maid outfit (man I hope Takeda releases Maid Arika's standing poses) and an actual game to play. Maybe a little sprite work too, depending on if Takeda uses the RPGmaker sex sprites.
Writing isn't going to be too complicated with the routes for the girls. It'll just follow his usual formula from the doujins. Not that that's a bad thing.
Really, the only thing I'm curious about (other than how many scenes/cg we will get for each girl) is how extensive the "non-NTR" route will be. Will the MC get any action at all, is everything unavoidable, can you choose which girls to save and which to make fall, etc. The girls routes, while I know will be exceedingly fun to watch, hold no real mystery to me. It's seeing how the MC will react, whether or not Takeda will go with the whole "Stay oblivious" or "Despair when he discovers his lovers corrupted" or even "Broken/Hypnotized into being their cleanup boy/bitch" or some other option is what intrigues me. Seeing a beta cuck's reaction to the NTR (which depending on how much input the player has, may or may not be your fault) is a big appeal of NTR.
Other than the hot scenes of the 3 bitches getting corrupted. I am really looking forward to seeing more sample cg of the girls and for when we finally get penetration scenes for Arika and Rietta.