If you mean, what is Sumata (Japanese: literally: "bare crotch") is a Japanese term for a non-penetrative sex act popular in Japanese brothels.
Sumata is a form of frottage, performed by a female sex worker upon a male client. The sex worker rubs the client's penis with her hands, thighs, and labia majora. The goal is to stimulate ejaculation without penile-vaginal penetration. This activity circumvents the Anti-Prostitution Law (?????, Baishun B?shi H??) of 1956, which prohibits sexual intercourse for money.
The rise in popularity is analogous to the growth in popularity of Western brothels and strip clubs offering non-penetrative lap dancing.
