I wanted to recommend JoliNails, for a nail salon birthday party.
My daughter celebrated her 6th birthday party at JoliNails. They have a party room, which the kids played games and ate cake. The girls went to the nail salon area in pairs, with their mothers for pampering. It was a HIT.
The staff is bilingual and great with kids.
The party room is at JoliArts, www.joliarts.jp the 1st floor of JoliNails Salon, so the staff there are professional instructors and caregivers.
Tuesday-Sunday open 10-8PM