Are you talking about the Spa World ?? Please refer to their website for details (admission fee, special feathers) as follows.
Spa World http://www.spaworld.co.jp/index.html
Inside, they will provide everything like towels, shampoo, shower gel, etc.
When you enter the Spa World, they will give you magnetic wrist band for recording your spending so when you check out, you just need to pay at the check out point.