Ecchi

Fan service is found in many anime, in many forms. When the service has a distinctly sexual slant to it, and it appears to be a major focus of the show, then it’s safe to assume you’re watching ecchi.

The word “ecchi” is used by English-speaking anime fans to refer to refer to soft-core pornographic or sexually suggestive anime and manga. This is a western invention; in Japanese, it is a catch-all term for all things anyhow sexual in nature, not being limited to porn, but also not really considered a “milder” term, as it may also refer to sexual intercourse itself. The term “ecchi” in Japanese comes from the pronunciation of the letter “H” in English, which is rendered into Japanese syllabary as エッチ, which in turn is transliterated in the English alphabet as “ecchi” or “etchi”. It is not, as many believe, short for “hentai” — that, too, seems to be a western invention. It is, however, nearly as misunderstood and misapplied a term as “hentai”.

The line between ecchi and hentai, from the western perspective over these terms, can be hard to draw at times; one good rule of thumb is: if it was aired on Japanese public TV at all, it probably wasn’t hentai. Ecchi usually features all the specifics to human anatomy that can only be found in anime, and generally avoids full nudity, instead abusing of panty shots. Hentai, on the other hand, will usually show full frontal nudity in some explicit form, including genitalia, and full, intimate sex scenes. At its mildest, ecchi is composed of double entendres, big misunderstandings, and sexual farce; at its most explicit, it is still in the realm of softcore pornography, with full breast shots, full back nudity and similar content, but no display of genitalia. Another good way to distinguish the two is looking for animated sex scenes; if one is found, you have generally left the genre entirely, though a few borderline exceptions apply here. For AniDB’s purposes, the distinction between explicit ecchi and actual hentai is simple: if it was sold with a 18+ restriction in its country of origin, it is hentai; if it was sold without it, it is ecchi.

Source: TV Tropes