Abuse puppy is mostly right about how to play the game. Here is the way I beat it:
First of all, this isn't one of those games where you have to make all the right choices all the way through to beat it. Whatever scenes you unlock with your choices, those scenes will count toward winning the game in the end, even if you get ejected from the game (which will happen each time you complete one of the nurse's storylines). And each scene you manage to activate can be accessed later on the CG menu and there's also some kind of Sequence menu right below it.
When trying to complete a nurses storyline, I recommened saving the game before each choice in the O.R. - The choices in the O.R. are MOST important. Although not every choice will raise the girls body modification percentage, every choice does unlock new images in the CG gallery. Sometimes the differences are minor, like on the red-head one choice makes you spank her bottom til it's red and one does not, so if you don't make that choice you won't have access to a pic of her slightly reddened ass later. For the blonde, certain choices might not earn you points, but these choices do unlock images that are more B.E. than P.E. in her storyline. Saving the game at these option screens allows you to jump back quickly to make the alternate choice and unlock more scenes and it works that way for all the nurses.
It does appear that getting all four girls (red, blonde, green and purple) to at least 90% is the way to beat the game.
[SPOILER]
Beating the game causes a sequence involving the purple-haired doctor lady that appears throughout the game. I don't know any Japanese, but the way that your character keeps leaving the O.R. and coming back to a surprise, I suspect it is the purple-haired doctor lady who is actually performing the modifications on the nurses, not your character (who it sounds like they call him "Sensei", btw). It does appear that you need less than 100%, perhaps 90% completion on each girl to get the game winning sequences. Getting each girl to 100% however also unlocks a special "winning" sequence for each girl. Those who have seen the Bondage Game anime movie based on a game by this same company will recognize the same plot device for the big winning sequence, where some blonde guy who appears to be paying to uh...use the modified nurses...and later decides he'd like to have a go at the purple-haired doctor lady, who wasn't originally part of the deal.
The red-haired girl's mods are ass expansion, breast expansion, and there is some toilet play (she seems to have some sort of crap pumped into her breasts and her bladder forced to bloat in one scene). The nurses demeanor is submissive.
The blonde girl turns out to be a hermaphrodite apparently, and has her equipment progressively enlarged throughout her storyline. At one point, your choice will either put her on the path to having a gargantuan dick, or to have huge breasts with dick-sized nipples, which she uses to fuck a couple anonymous nurses simultaneously. There's also a scene with three guys jerking off her dick and her nipple-dicks while she is restrained. Of all the nurses she seems happiest with her modifications.
The green-haired nurse's story is straight up forced B.E. and lactation. She's the bustiest to start off with, and she is not to thrilled with the progressive enlargements forced upon her. There is some degree of bondage, as is the case with all the nurses. Every time you think her storyline might be over they make her even bigger. By the end of her storyline, the sheer massiveness of her breasts appears to have broken her fighting spirit, and she does little more than cry out as she's milked like a cow. Some images have been posted to this forum, but not the pic of her at her biggest size. You'll feel better playing the game and earning that image through hard work, in my opinion.
The fourth girl looks suspiciously very young, but I suppose she's old enough to have a nursing degree...I still have my doubts. Her theme seems to be extreme pussy stretching and stuffing, and I guess what they call [censored] sex cause she looks really young and they have her flipped around in various positions like a rag doll. Not much else I can say about that.
The bonus sequences for winning the game are pretty self explanatory. Each CG image in the CG gallery has multiple layers that are unlocked by choosing different options in the storyline. If you haven't unlocked all the layers of a particular image, the thumbnail appears to be slightly grayed (thanks for noticing that Cheviot). The link beneath the CG gallery allows you to replay scenes from the O.R. without having to actually play the game. The link beneath the scenes gallery is the soundtrack! Awesome music! The link beneath the soundtrack is some weird stuff...looks like "inside" jokes and maybe some behind the scenes info from the cast and crew. I don't know Japanese so I don't have a clue.
Of course my goal was to unlock every CG image and every sequence so I can view them at my leisure. Other' might not be so inspired, and others who are that inspired might just screen cap the whole thing for the rest of you. I haven't beaten a game in a long time so I feel like I've accomplished something, and no game I've ever played has had such great rewards at the end!
