ahegao ― the facial expression made during orgasm

ashikoki (足扱き, 足コキ) ― using the feet to manipulate a sex partner's penis. The feet are often clad in pantyhose, cotton socks or even high heels. The pleasure is said to be as much psychological as physical[1].

bukkake (打っ掛け, ブッカケ) ― usually in group sex, ejaculating onto the body or face of a sex partner. The United States Department of Justice has defined Bukkake in a criminal complaint as: a genre of adult movies that includes depictions of many adult males ejaculating on a single female[2].

chikan (痴漢) ― molester

enjo kosai (援助交際) ― compensated dating (lit: assisted company), usually a euphemism for teen prostitution[3].

futanari (二形、ふたなり) ― Hermaphrodites (lit: 'double form')

fuzoku (風俗) ― A word which originally just meant "culture," it now also refers to "sexual culture" and specifically to soaplands, image clubs, pink salons and so on[4].

gokkun (ゴックン) ― This is the sound of swallowing to the Japanese. Gokkun movies usually feature a girl who after performing oral sex to one or several men plays with the spent sperm before swallowing it, those girls are called Gokkun Girls.

hentai (変態) ― literally, "depraved" or "abnormal," typically used (outside of Japan) to refer to pornography in anime or manga.

image club ― a type of brothel in which females dress in various types of clothing (race queen dresses, schoolgirl uniforms, etc.) and perform sexual favors according to several different fixed courses or "menus."

lolicon, rorikon (ロリコン) ― a fetish for underage girls, paedophilia. The person with this fetish.

nakadashi ― fetish for intravaginal ejaculation; creampie.

netorare ― fetish for being cuckolded. ex. A woman cheats with her significant other's knowledge and treats him poorly.

netori ― fetish for cuckolding someone. ex. The protagonist steals a woman from another man.

panchira ― upskirts or panty viewing. According to sociologist Soichi Inoue, the interest dates back to the 1920s when Japanese women first adopted western-style undergarments, but "panchira culture" became more overt in the 1960s[5].

paizuri ― tit fuck

pettanko ― flat-chested

pink salon ― A type of brothel specializing in oral sex. It has been reported that pink salons are among the most demanding places to work in the Japanese sex industry, with workers serving up to 50 customers per day, but the pink salons also function as gateways to more lucrative work in soaplands[6].

seme (攻め) ― top
shibari ― bondage[7].
shimapan ― the classic set of blue and white striped panties

shinju (真珠) ― breast bondage

shotacon (ショタコン) ― fetish for underage boys

soapland ― a type of brothel where men can be bathed by and can bathe with female prostitutes.

tamakeri ― A fetish that involves men being kicked in the testicles. ballbusting. [8].

tekoki ― The same as ashikoki, but with hands instead of feet.

telekura ― an abbreviation for "telephone clubs", telephone-based dating services that often serve as fronts for prostitution. Advertised through flyers and stickers throughout Tokyo, the clubs are used to arrange meetings, generally between young women and older men.

uke (受け) ― bottom; receiver; abbreviation of ukemi
urabon (裏本) ― an illegal book containing uncensored sex photos

yaoi ― A sub-set of ero (erotic)/hentai, sexually explicit comics (and doujinshi) about the love between males[9].

yuri ― female/female homosexual comic or anime (lit: Lily)

https://en.m.wiktionary.org/wiki/Appendix:Glossary_of_Japanese_sex_terms