It's hard to say precisely where this idea came from, but I think parts of it come from my (rudimentary) knowledge of the Harvest Moon series, an old walkthrough for Dragon Warrior Monsters, and the trailer for Galaxy Angels Z on one of the season 1 Ranma 1/2 DVDs.
The basics of it is this; a group of computer studies students have been designing their own videogame for a project (or simply for the hell of it, whatever). Being, to put it bluntly, something of nerds, they've chosen to make a date-sim (at least at core- see below), and now the thing just needs someone to test it. As it's kind of pointless for the creators to be the playtesters (beyond the risk of bias, they also designed everything so they know how to crack it), they decide to ask another student to do it for them... Ranma Saotome. While he is, and they acknowledge this, almost as clueless about girls as they are, he's also already *in* a tangle of relationships, so who better to try his hand at this creation of theirs?
They eventually manage to persuade Ranma to give them a hand and take a look at it, so he takes it home with a spare system and TV, so he can practise it in private (he, naturally, intends to keep its existence as secret from Akane and the others at the Tendo Dojo). Setting it up in the dojo (or possibly somewhere else more suitable) he finally sits down, boots it up, takes a look at the game manual (accessible from the "START" screen) and finally turns it on... and is promptly sucked into the game.
Now, I know what you're about to say, and I'll clarify things right now: unlike the cliche, Ranma *isn't* trapped in the game. As soon as he fulfils a certain condition (not sure what just yet), he is able to enter and exit the game as he likes. Ranma figures that this "gimmic" was part of the designers' intentions, so he never speaks to them about it (whether this 'mini-universe' aspect was intended or not is something I'm also unsure of), and resolves that, no matter how realistic it is, he promised to playtest it for them and so that's what he'll do.
I see two "branches" for this story; one is that Ranma's experiences in the 'game' make him more understanding of girls and romance in general, which helps his own tangles in reality. The other, somewhat darker possibility is that Ranma starts to *prefer* the game-reality so much that, eventually, he tries and maybe even succeeds in relocating there permanently, thus cutting off all ties with his former life.
So, what do you folks think? Any possibilities in developing this as a real story?
To keep my thoughts straight, the actual game is a somewhat confusing (at this early stage) mishmash of a date-sim and an "explorer" (the kind of RTS/RPG hybrid genre that games like Pokemon and Dragon Warrior Monsters belong to). The player chooses one of several "worlds", each with a different theme (so far I have only two; Horror and Fantasy), and starts in that world with a small home- really little more than a squat in an empty plot. Each world has three girls for the player to choose between to pursue romantically, as well as three "hidden" girls that can also be pursued once they are unlocked (kind of like wooing the Harvest Goddess in one of the more recent Harvest Moons).
The player is able to stroll around the "world" (really a town) and interact freely, and this leads towards the RPG elements- scattered around the world are 'rifts' that lead to 'dungeons'. I'm not sure yet whether or not the dungeons have enemies or simply places to explore and puzzles to get around, though the vague idea is that the player can have one of the love interests accompany them into a dungeon and that each one has her own special abilities that can help with exploration. The player explores these dungeons for treasures; this is basically how they generate the "cash resource".
Cash is used to expand, upgrade and otherwise improve the player's "base" or home, and this helps progress the game- certain upgrades are needed to unlock specific events, like revealing a secret girl or opening a certain area of the town. Plus it helps make things a little easier to woo the player's chosen girl.