Flint the Time Detective Wiki

Tokio (大和トキオ, Yamato Tokio) is the twin brother of Yamato Sora and was introduced as just "Tokio" in the Bros. comics originally.

The wikia has the following pages on him;

Etymology

His family name of "Yamato" is a name of a province that exists in Japan, it is also one of many names used to refer to Japan itself.