Nihon (日本) is the most common name for Japan in their own language, the one we can often hear in original commentaries of the Samurai Blue matches.
Sakka (サッカー) is the Japanese term for association football, derived from the English word "soccer". That stayed, despite football being the most common version internationally.
And finally, Mirai (未来, みらい) is a Japanese word meaning "future," representing hope, promise, and the time yet to come — the same that will come for Japanese football.