So this is something I wrote a year or two ago, maybe three, when in a burst of creativity I was actually able to write some stuff and this is the result of taking the Chained World - SM thread that was on Anime Addventure too far. In short Genma and Ranma have returned after 10+ years away in a fantasy world after it got invaded by Cthulhu-type monsters with several million refugees, including Ranma's massive (Slave) harem.
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Shinobu didn’t know what to make of her new sister, or the new sisters that the other girls at the Hinata Dorm. She’d seen the news on TV last night about a portal to another world opening up and people fleeing through it to escape from the monsters attacking their world before she went to bed, but she’d never thought that it meant she’d be meeting herself when she got in the morning.
And yet that was exactly what had happened right before everyone had to leave to go to school, some man from some part of the government had shown up to drop off copies of everyone expect Sempai. Had Sempai simply not be born in this other world or had something happened to the Sempai in this other world? She didn’t know which idea scared her more.
The new Su-san was probably the least different, or maybe the least shocking, as she looked and acted like the foreign princess that she was. Kitsune-sempai was wearing the same sort of outfit that the girls who worked in those cafe’s she wasn’t allowed to visit because they where hentai and had that worn out look that Sempai always had, or that Kitsune-sempai had after she’d been forced to get a job to pay for her drinking and gambling. If this Kitsune-sempai wasn’t able to mooch of anyone that was just fine with Shinobu. Naru-sempai was wearing a leather bikini and carrying a big axe, her skin was covered in small scars and she had this haunted look about her.
“Here’s your tea, Motoko-onee-sama.” Said her new sister, placing a cup of tea in front of the new Motoko-sempai.
“Thank you, Shinobu-chan.”
Which just left her and Motoko-sempai. Physically Motoko-sempai didn’t look any different and she was still wearing shrine priestess outfits, where she was different was her demenior, the new Motoko-sempai was serene, at peace with both herself and the world, like a samurai, or maybe samurai-princess, out of some drama. The only explain Shinobu could think of for the Motoko-sempai’s change was her pregnancy and the impending motherhood that came with it. But that left Shinobu even more curious over who the father was and why Motoko-sempai decided to become pregnant. The only man that Motoko-sempai spent anytime with was Sempai, but if Sempai had gotten Motoko-sempai pregnant why wasn’t he here to look after his wife? Maybe her sister hadn’t approved of the marriage? But then why was Motoko-sempai so happy?
Herself, the last new arrival and by far the most changed. She was a catgirl, in a sexy maid outfit, not a cute one but a sexy one. The weirdest part of the whole outfit was the collar she wore. It wasn’t that it stood out but rather how well it worked, after all she was a catgirl. Unfortunately the same couldn’t be said the collars everyone other then Suu-san was wearing. Some effort had been for the metal one Motoko-sempai and it was a nice red that almost matched her hakama, but the leather didn’t match Kitsune-sempai’s outfit at all and the colour and styling where off for Naru-sempai.
“So Keitorou, with twice as many girls living here now, does that mean you’ll have twice as many incidents?” Teased Mistune, causing Mitsune and Naru to look even more upset and Motoko’s face to flash red with fury.
“So us running around trying to kill a man because he accidentally saw us naked in funny to you, Konno-san?” Fumed Motoko.
“Sure is, luv.” Quipped Mitsune, causing Motoko to stand up and draw her sword, some how causing Mitsune’s clothes to fall to pieces around her, causing her to cover herself with her arms. “What the hell, Sword-girl.”
“Maybe this will teach you that your ‘fun’ is dangerous without killing Urashima-dono.” Replied Motoko. The thought that Kitsune’s actions resulted in her Sempai dying was too much for Shinobou and she passed out.
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So in short, Mitsune does something that causes Motoko and Naru to kill Keitaro, as a result the three are sentenced to slavery. Despite Suu offering to pay for his resurrection he stays dead. Mitsune gets sold to a woman who runs several very risque maid cafes, Naru ends up a gladiatorial slave, billed as a barbarian. Motoko is brought by Ranma for her sword skills, he's kind-of found himself responsible for defending the world from all sorts of menaces as a result of owning the Senshi, and her skills would be useful that, but Rei invokes a promise Ranma made her, and Motoko ends up carrying her child (Motoko is actually the father of her and Rei's child) and responsible for the physical protection of the next generation of Senshi.
Shinobu's parents decided now was the best time to put her and her sisters (The three of them identical triplets[Shinobou, Sassmi, and Sakura]) up for sale (they always planned on this, and in fact it's the reason they had them, after all who wouldn't want a trio of cute cat girls? And then they would live off the profits) and Ranma ended up buying them after some prodding from some friends.
Suu went back home Keitaro died.
If I was writing this today it would be different, there would be language barriers, so the only two Hinta girls who would be at the Hinta-sou the first day would be Motoko and Shinobou as they have the chance to learn Japanese off of Genma and Ranma as part of a back-up plan while the others are languishing in a refugee camp until communications can improve. But they may be joined by Motoko's three friends if they're silly enough to turn themselves into slaves in an attempt to 'protect' Motoko.
Naru isn't likely to win the fight for Keitaro in this timeline because Shinobou has people supporting her, to whit the Sailor Senshi, who are going to encourage her to make a move and help out by offering to turn her into a Succubus, which in this case is a human (or elf, or whatever) transformed by the Elemental Plane of Love
As for why the duplicates are at Hinta-sou, well story and the government is off loading duplicates onto their local counterparts to cut down on costs.