Yes, the sentence does require an article before the word Japanese. It's because we don't talk about team.
We talk about a team or the team. The choice would depend on whether the writer thought that the intended audience were familiar with Samurai Blue. If yes, then use the definite article. If no, the indefinite. If unsure, use either one.
And the expression is NOT win to the round. It is win through to the round or got through to the round.
Finally, NOT the round of 16, just to round 16 (or possibly the quarter finals etc, depending on how many rounds there were).