Was this a local variant of art deco?
@acb
Hi there! You seem to be very knowledgeable about architecture.

This building is part of "Azabudai Hills," a recently developed compact city in Tokyo.
https://www.azabudai-hills.com/index.html

The specific section of the building I photographed is a school.
https://www.azabudai-hills.com/school/index.html

The design of this lower-level structure was created by Thomas Heatherwick from the UK. It features modern architecture with a beautiful and extensive use of curves.
麻布台ヒルズ - Azabudai Hills

麻布台ヒルズのコンセプトは「Modern Urban Village」。緑に包まれ、人と人をつなぐ「広場」のような街です。いま世界が注目する新しい都市の豊かさを、国際都市・東京の中心で実現します。

麻布台ヒルズ - Azabudai Hills
Ah. I’m guessing Heatherwick was drawing on art deco and streamline moderne, possibly examples built in interwar Britain, though with a contemporary twist. (The curved window panes are very 1930s, in my opinion.)