Hello, welcome to the forums! 
This is very similar to this topic.
If you’re wanting a specific physical key set for Japanese, that could be different. It might be a matter of having one custom ordered/printed. Given how modular things are, and the fact that it is coming from an Asian market, I wouldn’t be surprised to see alternate keys with different characters printed on the keys.
Although, given the name, I’m fairly sure the device is aimed at a developer/coder, where you would usually be typing commands with a standard key/character set.
I doubt there would be much use in using the devterm for web browsing, messaging etc. A mobile phone is better at that nowadays.
What I think would be beneficial would be a Dvorak layout, given its diminutive size. I can’t imagine having a good time trying to use two hands; but single hand use would be ideal.
@moderators - do you think it’s worth merging this topic with the one quoted above? They’re practically the same.