Okama

The first real okama to appear in the story is Bentham, also known as Mr. 2 Bon Kurei, who first appeared as an enemy to the Straw Hat Pirates, but ended up being friends with them. The ruler of the Kamabakka Kingdom is Emporio Ivankov. Kamabakka Kingdom is the okama kingdom, (which Sanji has the greatest misfortune to be sent to) and even the animals on the island are shown to be okamas.

Appearance
The okama depicted in the storyline generally wear items that are normally only worn by women and tend to wear these clothes regardless of their body shape or suitability. Many of the clothing is therefore a abstract exaggeration of what women might wear, often looking bizarre and base on normally enhancing the female sexuality when worn by women. Not all are clean shaven and most do not seem to hide their true masculinity underneath these female clothing.

The Newkamas wear clothing more suited for their body types. Due to being more free because of Emporio Ivankov's Devil Fruit, there are also females as well as males in their number, though they might not have necessarily been the gender they were born as. Unlike the island's okamas, they wear a wider variety of clothing such with some even modeled on animals.

Beliefs
Unlike the Kuja, who are born on their island, their kingdom is a place where "those with a heart of a maiden" gather and therefore their membership come from across the world to learn the okama way. This is not just restricted to humans, but to the animals of the island too. They do not see the issues related with being an okama that others see, even though their own status as okamas can be off putting to others.

As Sanji explained, he wanted to be more then just friends with women. However, the concept of loving a woman is not part of their beliefs as they wish to only befriend them, not to love them. They are not without understanding of the image of a handsome individual but are very open on their feelings to the point where some felt Sanji's rejection of their advances was only because he was being shy.

Each of the named okama integral to the story's plot development have shown to exist as the opposite gender. Bentham can become a female using his Mane Mane no Mi abilities, and Ivankov uses hormones to change his and Inazuma's' gender. These individuals in particular are dedicated to "the okama way".

Newkamas
This is a group of okamas led by Emporio Ivankov, and they were all former Impel Down prisoners.They represent a more updated version of the okama belief. Unlike regular okamas, newkamas claim to go beyond the concept of gender since almost every one of them has changed genders thanks to Ivankov's Horu Horu no Mi, which allows them to experience life in both male and female bodies.

Overall Strength
The island is home to the practition of the Okama Kenpo martial arts and also has 99 Masters of Newkama Kenpo. Okama are feared both for their mastery of their Martial Arts and for their status as Okamas.

Being former prisoners, all Newkamas are all very strong fighters.

Imprisonment of Emporio Ivankov
For being a revolutionary commander, he was arrested and sent to level 5 of Impel Down. Iva and many other level 5 prisoners disappeared into level 5.5, until he aided Luffy in escaping from Impel Down.

Translation and Dub Issues
Okama is Japanese slang for homosexual or transvestite. Literally meaning "a pot, a kettle" this word, always with the honorific prefix "O-" refers to a gay man, especially one who is viewed as effeminate or a drag queen. Can be pejorative. The word originated in Edo period slang for the anus.

Trivia

 * Newkama is a pun between "new okama" and the word "newcomer".
 * Bentham and Iva are the only known okamas to be able to switch genders on their own.
 * As of yet normal humans are the only one of the major races to have been shown as okamas.
 * Eric is a filler mercenary who wields the Kama Kama no Mi. Due to the "Kama" part of his powers, Luffy keeps calling him an okama, much to Eric's frustration.
 * Traditionally, it was much harder for men to pretend they were a woman and it was much easier to spot the ones that failed to look female and the look of the okamas is a joke towards their obivous male appearance many would end up with. However, the Newkamas are like the modern transvestiate, who is often much harder to spot thanks to hormone treatment and plastic surgery. This is also often the source of the term "trap" in which the female appearance is so deceiving that other men will fall for them without realizing they are a man.
 * Despite the fact that the Okama are based on a homosexual men stereotype, it isn't stated if they're actually all attracted to their "original" gender, or rather just embracing a certain lifestyle, regardless of their preferences.