Dial Q o Mawase!
ダイヤルＱをまわせ！ - Japanese spelling
The mahjong itself is strictly a recreation of the traditional Chinese board game. However, after each round the player wins, the opponent will remove a part of their clothing, until eventually they are completely nude. After defeating an opponent, they will give you the phone number of the next target that must be interrogated, which doubles as a password. There are six different opponents to play against in total.