Forget the spa, when in Japan you go to an onsen.
Jakotsuyu Onsen

The legend says that in the year 628, two brothers fished a statue of Kannon (goddess of mercy) out of the Sumida River, and even though they put the statue back into the river, it always returned to them. The temple for Kannon was completed in 645, making it Tokyo’s oldest temple.
In Tokyo there is a whole industry of kawaii (cute) cafe concepts.