[hueving]

Japan isn't really ahead of Singapore in this regard due to its position much further north. The heat in Singapore is unbearable inside a building without a/c during the day. Putting on a casual shirt will hardly help in that situation.

[6nf]

It does help when you go out to lunch etc, even the 5 mins from building to building can be pretty sweaty

[dogma1138]

Japan isn't in the tropics, south of Japan does get quite warm but Tokyo is on the 36th parallel it's not much warmer than many US cities.

Japan does in general has a much stricter dress code than most other places with similar climate.