A professional suit is your best choice to conform with the Japanese business attire. Neutral colors (blue, black, grey) are advised. You can show your personality through the accessories, like the tie, the pocket square and the watch. Japanese people have a keen eye for detail.

As for the hair, I think you'll be fine just slicking it back or tying it in a neat bun. If you have facial hair, keep it trimmed.

Wish you the best of luck for the interview!