Mainly goes by 9259 (Kyu-ni-go-ku): a not-so-subtle sexual pun.
Fairly small and foreigner-friendly, however, both some understanding of Japanese and a Japanese Health Insurance card, are required for sign-up.
Has rule about couples not being allowed to play with single women (only other couples and single men).
Play areas are private (staff opens them for people who want to play, and door is kept closed).