Kei Kei no Mi

The Keiy Keiy no Mi is a paramecia type devil fruit that allows the user to make and control contracts and deals, making them a Contract human.

Strengths and Weaknesses
Through this fruit the user is able to produce contracts and make deals of most any variety. These deals must be made with two or more parties, and their must be some sort of trade, you can not receive something without giving something away. The party besides the user of the fruit must also be consensual or sign the contract in order for it to be set in stone.

Once the person has signed the contract every action specified in that contract must be done, and they must follow the rules set by the contract. If one of the parties should break one of the rules of the contract or go back on their promise a being summoned by the fruit known as "Tanpo" will come for that person or people and exact punishment. These contracts can come with some sort of specific punishment that should happen to anyone who would dare to break the contract.

Tanpo
Tanpo is a creature summoned by the user, and the medium by which the deals are made. He exacts vengeance on those who break the rules of a contract, but for the most part he is a passive figure following the user until the next deal is made.

Deal with the Beast
Tanpo is almost always a passive force only being active and useful when the user is making deals, but if need be the user can make deals with them self to use some of Tanpo's power. Little is known about the creature, but he is very strong and if the user chooses they can trade in some of their life span or something of equal value to tap into or use their incredible power.