Sensei's Teacup is a tea shop where you can get 4 different types of teas (they might have been drugged, are they even FDA approved)
If you stay there, you won't appear on the arena battle.
There are 3 tables with 12 seats (4 per table) and all of them have a carpet.
Also you can see a lot of food on a table next to it.
You can access to this area by going into a teleporter on the Lobby.