Hentai is a japanese slang for being a pervert. In Japanese the word hentai is a kanji compound of 変 (hen meaning "change" "weird" or "strange") and 態 (tai meaning "attitude" or "appearance"). (Source: Wikipedia). People who dress wierd are often referred to as hentai. Franky was often refered by citizens of Water 7 as hentai for wearing only undies and unbuttoned shirt. The other meaning of hentai is used to depict adult content in manga (comics) & animation.