Warning this came to me in that period between being asleep and awake. It was written when I was very exhausted so may be disorganized. This is only one of many ideas I have had for Ranma fics. Also if I do write this things may change like I might find it more amusing for Ranma to lose instead of Nabiki (I just think in a long term battle like this Ranma would win for a variety of reasons (more stubborn, more used to these type of things happening, etc..) with Nabiki doing better in the short term.)
First off even though this has been done in the manga to a lesser degree Ranma is not as disadvantaged as he was before. In this instance Ranma is not going to fall for Nabiki saying she loves him (he is convinced she doesn't) and he's not feeling guilty for destroying her concert tickets or something. In this instance Ranma is mad at Nabiki and not staying on the defensive. Ranma is also going to use Nabiki's own strategies against her using the logic if she can do it so can he.
Ranma and Nabiki have several things in common. Both are willing to go to depths that normal people would consider insane to win, both have little modesty (Nabiki sun bathes without a top at least once during the manga and has no problem wearing revealing clothing), both enjoy manipulating people for their own personal gain and/or amusement, both generally don't think about the long term effects or possible consequences of their actions, both have pretty questionable morals, etc...
Fic starts out with a confrontation between Ranma and Nabiki. Ranma has gotten fed up with her taking pictures of him and decides that since they're pictures of him he should get some of the money. Nabiki says hell no, she took the pictures and it her money. Ranma counters that they are pictures of him and he should get the money. Nabiki says something like it's my money and there isn't a thing you can do about it. What are you going to do beat me up until I give it to you. Won't that look good the big bad martial artist beats up a defenseless girl. Ranma plays the blackmail card and claims that he's going to put these pictures of her all over the school. (Pictures are of her taking a bath and sleeping.) Nabiki says something like How interesting I bet that your fiancees will be really happy that your peeking on another girl. Ranma tears up and melts the pictures. Things pretty much escalate from there with Ranma and Nabiki having pretty much gone to war against each other and they make a bet the person who gives in to the other becomes the others slave for a month (Nabiki in this case is the overconfident one it is her idea since she seems more likely to make this type of bet). With both of them manipulating others to get at each other. (examples. Nabiki making things harder on Ranma by manipulating Ranma's fiancees. Ranma convincing Kuno that a lot of the things happening are Nabiki's fault. Nabiki convinces the parents to switch the engagement back to her so as to better annoy Ranma. Ranma not falling for her tricks and convincing the entire school that Nabiki is a massive pervert and a lesbian (can say things like she likes my girl form and why do you think she is always taking revealing pictures of girls. This also works with Ranma's fiancees so they start really annoying and bothering Nabiki and helps to alienate her from a lot of the girls at school) Ranma using his martial art skills so Nabiki has a whole bunch of seeming accidents that are really perverted like tripping and accidentally pulling down a girls skirt. Nabiki tries renting out Ranma again Ranma counters by renting her out (to clubs and such nothing perverted) using the simple logic if she can do it I can do it. Ranma still saves Nabiki from the fiancees and such but decides to charge her for rescues and when she refuses to pay Ranma allows Shampoo to beat her up a little nothing serious just some bruises. Nabiki out maneuvers and out manipulates Ranma a lot especially at the beginning (occasionally he'll get a good one) and eventually as it progresses and Ranma gets better at it while Nabiki is having a harder time at it because she doesn't know how to handle it and events happen to fast for her to take control of them. (Ranma's used to these type of things happening to him Nabiki is not.) Ranma ends up winning because he's more stubborn and there isn't really anything that Nabiki can do that hasn't already happened to Ranma in one form or another.
While this is occurring Ranma also has to deal with his normal day to day stuff just being made a bit worse because of Nabiki.
Ranma starts to plan ahead and think things through because he needs to in this type of battle. This has a major effect on Ranma's day to day dealings starting with him upping his training and preparing for things before they happen instead of dealing with things as they happen. (example, since he deals with spirits occasionally he prepares to deal with them by learning about them and making spirit wards. another example him making up new Ki techniques in preparation for a fight instead of waiting until someone uses them on him or he needs to come up with it during battle. A technique he may make up would be flying using a combination of old techniques. Iron cloth technique to make a blanket into a hang glider. Minor wind manipulation to keep it aloft. Use of Vacuum blades or Ki blasts to gain speed.)
Ranma also is dealing with aftereffects of the battle with Saffron in which he had thought Akane dead a number of times. Then there was the guilt in having killed Saffron who was a heat source and light for his people, sure he deserved it and he was reborn but that didn't make the guilt go away. Then being knocked unconscious and stuffed into a tuxedo for a wedding that he had no say in and doesn't really know if he wants or not. Then almost getting a cure for the curse only to lose it yet again. Rumors and innuendo at school. Part of the reason he is so into the battle with Nabiki is because it takes his thoughts away from thinking about the above stuff.
These types of things are also happening during this fic. Cramming for finals, which for some reason included reading an entire encyclopedia set and a thesaurus, while his mom kept him company by sitting in the room while sharping and oiling her Katana and Mrs Hinako draining his Ki when he left the room (Nabiki's fault mentions to his mom that Ranma is getting bad grades and shouldn't a martial artist do well in school). Happosai had been extra annoying having found an entire trunk of old magic stuff that he decided to test on Ranma (Ranma convinces Happosai that Nabiki should be targeted by asking for perverted training therefore making Happosai happy and using Nabiki as a training dummy). Kodachi blackmailing him with more doctored photos. Ryoga getting into an argument with Akari and blaming Ranma for it (lots of shi shi hakodens thrown)(this is just a coincidence). Cologne decided to put him through a torture test to see how much he had improved after hearing about the battle with Saffron. Kodachi, Shampoo, and Ukyo upping there pursuit on him by sneaking in to his bed and bath repeatedly (Nabiki helping them), Akane being in a state of near constant anger with Ranma for a variety of reasons (Some because of the other fiancees actions, because she knows about the terms of the bet, and because Nabiki is fanning her anger, etc..). Mouse upping the number of attacks on Ranma because Shampoo has upped her pursuit on Ranma, Kuno being Kuno, Principal trying to cut his hair, an average of two unknown people coming to challenge Ranma per day for reasons Ranma doesn't bother to find out or care, What little amount of a relationship Ranma has with Akane is going completely down the drain and Ranma decides that it may be better that way, Ect...
Part two would be about Nabiki's slavery (really bad for Nabiki because Ranma's mom, Happosai (owning a girl is like his biggest dream), and Cologne (for amusement value) decide to give Ranma advice - doesn't mean Ranma's going to use they're advice but it may influence him) and Ranma and Nabiki getting caught up in the Sailor Senshi battles somehow (probably a misunderstanding of some type with them thinking that Ranma's evil and enslaving others).





