This system is used when you are trying to get an NPC to do something for you. It's can also be used against PCs, but PCs always have more room to negotiate than NPCs do.
Step 1: Goals
Describe what your character's goal is. This must be something that is possible. For example, a goal of "Convince Seishiro Nobuna to stop fighting against Sumiko" would not be possible, but "Convince Nobuna to stop fighting against Sumiko for one year" might be. It's possible that the goal may evolve as the manoeuvring plays out; if this happens, then it's worth confirming that the new goal is still a valid one.
Step 2: Doors
"Doors" are a metaphor that represent how hard it will be to achieve your goal. Doors represent a character's inherent stubbornness, and also reflect how well aligned your goal is with their personality and ambitions.
The number of doors you must overcome is equal to the target's Willpower, plus:
One door if your goal would cause the target to lose less than 5 honour, or two doors if it would cause them to lose 5 or more honour.
One door if the goal is opposed to an Advantage or Disadvantage (e.g. making a Coward confront someone, or a Paragon of Duty betray their lord).
One door if the goal requires them to betray their lord, family or clan
Other doors may be added as appropriate
Step 3: First Impressions
The target's impression of you determines how often you can roll to try and open a door. By default, you start with an Average impression.
Improving the impression to Good generally requires appropriate roleplaying, but improving an impression to Excellent or Perfect will require successful dice rolls. The precise skill to be rolled depends on exactly how you're impressing them. For example, you might try to arrange the perfect party to meet them at.
If you can tie this is to an Disadvantage, you automatically improve their impression by one level. For example, giving a Rumourmonger some juicy gossip, or fulfilling a Fascination or Compulsion.
You can also give gifts, or bribe people to make them like you. If the target accepts your gift or bribe, improve their impression of you by one level. For example, giving an Otomo courtier an expensive bonsai tree improves her impression of you.
Step 4: Opening Doors
Opening doors: At each interval, you can make a roll to open a door. The precise roll depends on exactly how you're trying to win the person over, and doesn't have to be a social roll. For example, you might offer to repair someone's damaged armour and use this to open a door.
Helping your target: If your target has a goal or aim of their own, and you offer to help them fulfil this, it opens one door. You don't have to actually help; you just need to convince them that you will help. If an opportunity arises to help them and you don't follow through, two doors close.
Failure: If you fail a roll to open a door, you take a -5 penalty to all rolls to open doors or improve your impression. These penalties stack, and cannot be removed. It's possible for a failure to lower their impression level by one. If this reduces the relationship to Hostile, you cannot attempt to open any other doors until you improve the relationship.
It's possible for the overall attempt to fail irrevocably - this happens if you [dramatically fail] a roll to open a door, if the target realises they're being manipulated and feel betrayed or conned (merely realising you have an ulterior motive doesn't stop things; they have to feel betrayed), or if you spend more than a week at the hostile level.
[dramatically fail] is the mechanic in the system I've stolen this from - I'm not sure what the appropriate equivalent is. Perhaps just when it seems appropriate?
Step 5: Resolution
Once you open the final door, you achieve your goal! If the target is a PC, that player can negotiate a compromise to the main goal (e.g. rather than lending someone the Hundred Stances scrolls, you could let them visit Kanazawa and read them under your watch).
Example
Hida Honda wants to convince Kaiu Yotoshi to craft him a new tetsubo, after an ogre ate his last one. Yotoshi's Willpower is 2, and it will cost 2 points of honour to bump Honda's order to the top of queue, for a total of 3 doors. Honda only vaguely knows Yotoshi, and so starts with an average impression. Honda knows that Yotoshi will be at Winter Court and puts some effort into attending, and then shows off his knowledge of blacksmithing, which raises the impression level to Good. Honda mentions how impressed is he is with Yotoshi's skill as a craftsman. Honda succeeds at his Courtier (Manipulation) roll to flatter Yotoshi, and 1 door opens.
The next day, Honda talks to Yotoshi again, this time trying to impress the smith with how much glory Honda will bring for him by wielding one his weapons. Unfortunately, Honda fails the roll, and takes a -5 penalty to all rolls to open Yotoshi's doors. Because he failed quite badly (and made Yotoshi sound like an afterthought), the impression level drops to Average.
Honda decides to do some more research, and a friendly Bayushi points out that Yotoshi is a vain man, and is looking to get a supply of a specific ore for his next katana. Honda has a relative in the Yasuki, and tells Yotoshi that he can arrange to get the ore for him (which opens 1 door automatically; Honda doesn't have to deliver the ore, he just has to convince Yotoshi that he will. If he fails to do this in the agreed timeframe, 2 doors will close).
Honda then waits a while, before rushing to Yotoshi to tell him that Honda has been ordered to the wall. Honda confides in Yotoshi about how scared he'll be without a proper weapon in his hand, and generally acts as though only Yotoshi could possibly help him. Swayed by this appeal to his overwrought sense of importance, and a successful roll, Yotoshi's last door opens and he agrees to help the 'hapless' Honda by crafting his tetsubo soon.
If you don't have time to play nice with someone, you can try to force them to help you. You make a single contested roll, and you take a penalty of [5 x number of closed doors] to your roll. If you succeed, you achieve your goal. If you fail, the subject is immune to further social manoeuvring from your character.
You can make an Intimidation roll to force a door to open before making this roll; if you carry through on the threat, you open two doors. For example, if you threaten someone with a katana, you open one door; if you stab them with a katana, you open two doors. Different characters may be more or less resistant to intimidation, depending on precisely what you do.
You can also influence a group using this mechanic. The number of doors is based on the highest Willpower in the group, and the group will be given an Honour rating, and appropriate Advantages and Disadvantages to help determine how many doors you must open. If the group only meets occasionally, you'll want to improve their impression of you to high levels so that you can get them to agree to your goal in a reasonable period of time.
A few quick examples:
Yasuki R1 lets you know what would make a suitable gift to impress someone, and Yasuki R3 lets you find it. Yasuki R5 could be re-worded to cover automatically opening doors instead of/as well as the +5k0?
Doji R3 would also improve the target's impression of you. Doji R5 would open doors automatically.
Kitsuki & Bayushi techniques don't interact directly, but can give information to help you impress and open doors
Ikoma & Asako techniques don't interact directly
Ide R3 would improve impressions.
Note: This system is based on the Social Manoeuvring system in the God Machine Chronicles, just adapted for L5R's system.
Doji Courtier School
Rank 3: Clarification - If you acquire a gift for someone, it improves their impression of you by 1 level.
Rank 5: If you succeed at the opposed roll, ignore all Doors from Willpower [???]
An ally's Devotion has the following effects:
Devotion 1 - The target's effective Willpower is reduced by 1
Devotion 2 - As Devotion 1, and the target does not have any extra doors added for secret dishonourable actions
Devotion 3 - The target has 0 doors against you