In order to get this you need to take either Yui or Rina to Mahjong. Just reach rank D+ on them then when they ask where you want to go take them to play Mahjong (as tempting as it is to take them to karaoke). You do not need to win Mahjong but sadly you do need to finish one whole game. Either actually play the game (if you somehow are decent at it) or just keep pressing A thinking you are doing well then loose at the end or win in a freak accident. Either way when the mahjong game ends the date ends and the achievement will unlock.