Youkai (妖怪 Youkai?): nicknamed Kai (怪 Kai?) is a pirate who originates from the South Blue island, Baterilla. Here he was known as Cheung Po Tsai (チャンポーツァイ Chang Pao Tsai?). Although he lived a short amount of time here because of the World Government corrupting Baterilla, due to this the young boy decided to embark on a journey. He turned into a pirate during the beginning of his voyage, where he also changed his name to Youkai a pseudonym his previous comrades gave him due to the power of the devil fruit he consumed as a child. Youkai left his hometown for only one reason, to turn strong enough for him to be able of completely obliterating the World Government. This he considers his goal and is also the reason to why he turned into a pirate, believing they are the total enemies of the World Government and this being the most convenient way for him to reach his objective.
In one point of his journey, he consumed a powerful Mythical Zoan devil fruit known as the Inka Inka no Mi, with this devil fruit and his weapon, the Scissor Blade, Tyrfing (魔帝破剣 (ディルヴィング) Diruvingu?) which he has developed a sword style for known as Sentouryu (剪刀流 Sentōryu?) he has gained a notable reputation that have earned him the bounty of --- and the epithet of Spectre Knight (幽霊騎士 Yuurei Kishi?) because of his devil fruit powers, and extreme abilities that surpass any normal human’s along with multiple acts that are worthy of raising his bounty such as defeating a powerful Marine captain, defeating a pirate crew by himself, among others.
Youkai is one who follows the belief of "simplicity is best", a reason to his carefree persona, believing that complications are a "waste of time" for him. He is very air-headed, showing disinterest to most problems or affairs. In fact, when he is on missions, the pirate goes straight to his goal as quickly as possible. This is simply because of the reason that, Youkai is one that is always in a hurry, wanting to find the One Piece as quickly as possible. He is said to embody the definition of a pirate, a person with the goal of becoming the most famous, no matter what, someone who has ambitions.