Okama

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. 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. 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.

Beliefs
Unlike the Kuja, who are born on their island, the Okama cem from across the world to gather on their island. This is not just restricted to humans, but to the animals of the island too. They do not see the issues related with being a 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.

These opinions are most notably expressed by the barers of Devil Fruits which allow them to break free of the Gender barrier such as the Meme Meme no mi

Newkamas
This is a group of okamas led by Emporio Ivankov, and they were all former Impel Down prisoners. 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. All Newkamas wear revealing effeminate clothing and they are all very strong fighters due to having been former prisoners, with some even retaining their gruff appearance.

After escaping Impel Down, they followed Iva to Marineford to help Luffy save Ace, even though the war ultimately ended with Ace's death. The Newkama cheered Luffy on for a full recovery, and then went with Iva back to Momoiro Island.

Overall Strength
Bentham is a practitioner of the Okama Kenpo martial arts. He also wields the Mane Mane no Mi, which allows him to physically transform into other people, even other genders.

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.

Trivia

 * Newkama is a pun between "new okama" and the word "newcomer".
 * 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.
 * Bentham and Iva are the only known okamas to be able to switch genders on their own.
 * As of yet 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.