Kenji has kidnapped Hisao, barricaded himself in his secret base on the roof, and threatens to throw Hidao down unless his demands are met. No police. The girls must fight each other until KO, and only the strongest one will be allowed to fight him for Hisao. And if he sees anyone pulling punches he will also kill Hisao too.
So, as characters then, Emi, Rin, Misha, Shizune, Hanako, Lilly, Miki (unlockable) and Kenji (unlockable). 8 characters is good enough for a reasonable fighting game and it gives 6 or 7 rounds of fights in single person mode. Or, or 8 if everybody also has to fight their own "clone". I don't think need Kenji needs a robot or anything. Just let him fight with his scarf, and his huge glasses as his weapons. After all he's scary enough by himself, pushing people from rooftops.
What the introduction and stages would look like? Something like this, just a rough sketch, improvements welcome:
[Introduction]
(Kenji in front of the 6 ladies)
Kenji: "Good! You are all here! So glad you could make it! Today is the day when I will overthrow the feminist conspiracy! Look there!"
(Cut to hisao hanging in a cage precariously from the school's roof.)
Kenji: "I have seen what you have been trying to do! But I won't stand for it! If you want to save Hisao, you shall fight each other one by one until knockout!
Then, the strongest of you will challenge me!"
(Cut to Kenji showing his remote control.)
Kenji: "Don't try anything funny or I can't guarantee his safety! No police! And if I see anyone pulling her punches... I'll turn Hisao into a pancake!"
(Kenji running off to his rooftop hideout, leaving a live camera behind).
Kenji "So, let the tournament begin! Hehehe!"
[Shizune's Stage, the Student Council room] (Misha is in the background signing, unless he is fighting)
(Before fighting)
Shizune: "[I love a good competition!]" (She also says this in the beginning when you are playing her.)
(Facing Misha)
Shizune: "[Shut up Misha!]"
(if she wins)
Shizune: "[I love winning!]"
(if she loses)
Shizune: "[It hurts to be defeated, but I will never give up.]" (She also says this when defeated if you're playing her.)
[Misha's stage, also the student council room]
(Before fighting)
Misha: Waahahaha! You may not think so, but I'm strong too! Waahahah!
(Facing Shizune)
Misha: "[Don't be so hard on Hsiao and me!]"
(If she wins)
Misha: "Wahahaha! Bet didn't see that coming!"
(If she loses)
Misha: "Eh? No way!"
[Lilly's stage, the Tea room (it's small, so it's very tight fighting)]
(Before fighting)
Lilly: "I can hear your every move!"
(Facing Hanako)
Lilly: "I'm sorry Hanako, but it's for Hisao's sake!"
(if she wins)
Lilly: "I'll save Hisao no matter what!"
(if she loses)
Lilly: "Please go save Hisao!"
[Hanako's stage, the Library]
(Before fighing)
Hanako: "I want to do something for Hisao too!"
(Facing Lilly)
Hanako: "I... I don't want to fight you..."
(If she wins)
Hanako: "Sorry... Igottogodosomething!"
(If she loses)
Hanako: "I... I'm just useless..."
[Emi's stage, the track]
(Before fighting)
Emi: "I'm the fastest thing on no legs!"
(Facing Rin)
Emi: "Hey, it's no big deal right?"
(If she wins)
Emi: "See, I was too fast for you!"
(If she loses)
Emi: "I let my guard down..."
[Rin's stage, outside of the wall she painted]
(Before fighting:)
Rin: "It seems like we have to fight. Or something like fighting, at least."
(If she wins:)
Rin: "I'm surprised I won, since I'm unarmed."
(If she loses:)
Rin: "I'm seeing stars in broad daylight. Again!"
[Miki's stage is also the track, since she's hidden]
Miki: "Everyone forgot about me? But I also want to save Hisao!"
(If she wins:)
Miki: "Another one struck down by the fist of fury."
(If she loses:)
Miki: "It all went out of hand."
[Final Stage, on the roof of course]
(Kenji puts the remote control away to have both hands free for fighting)
Kenji: "You are the strongest of all girls here, but you fell right into my trap! I will beat you, take your DNA and clone you for my army to fight the feminists!"
(If he wins the final stage)
Kenji: "From today, the final battle against the feminists shall begin! An Hisao will be my lover forever! Hehehehehe!"
(If he wins another stage)
Kenji: "Your DNA is mine!"
(If he loses)
Kenji: ""Beaten by feminists? Impossible!"
(what the girls say, also if they face Kenji in their own stage)
Shizune: "[I won't give up so easily!]"
Misha: "Waaahaha! Stop being silly!"
Lilly: "It's sad to see you finally lost control! Let Hisao go!"
Hanako: "I... I won't let you hurt Hisao!"
Emi: "Stop running away, I'll catch you!"
Rin: "How did I get into this again?"
Miki: "You may have all other girls beat, but you've forgotten about me!"
(On winning the final stage)
Shizune: "[You forget that I never lose!]"
Misha: "Waaahaha! Hisao, let me comfort you this time!"
Lilly: "Finally, this madness ends. Hisao, I will not go away! I will stay here with you forever!"
Hanako: "I... I was able to help Hisao! Hisao! ... *hug and kiss*"
Emi: "Let's tie him up in the equiment shed! Hisao, I'll open up to you from now on!"
Rin: "What a weird boy! I gues I better get Hisao out of there..."
Miki: "Hisao! Don't ignore me again! I waited for you for so long!"
Ah, Yuuko could be also a nice hidden character, her stage being the library too. I'll leave her lines up to someone else.
Actually, I'm starting to like this idea a lot. If people agre this is the way to go, then I'd like to volunteer for programming a bit and writing the scenario, if that's OK. You guys should set up the code repository on github or sourceforge so we can share it easily.