It is a possibility that Japan might win against Belgium. But, I trust my hunch, the one that predicted the unlikely Portugal winning the Euro 2016. We used to gauge a team's strength by looking up their history, their squad lineups, and recent performance. But, I think, seeing how they play in the tournament and changing your views on them are rarely done. Is Mexico defeating Germany means they are good? Well, they follow that "park the bus" routine, and got so many wasted chances (6 from Layun, none were on target) because apparently Germany only played 2 defenders. Back in Euro 2016, I saw the talent-laced French squad unconvincing and their unexplainable penchant for placing the then extremely lazy Giroud (he is quite hardworking now). They killed the individually inferior Germany by 1-on-1 dueling each of them.
Belgium is a team's team despite its celebrity star player lineups, because they have no reputation too big to handle. Everyone will play their best, and I am sure that they have all the requirements to reach the final. England, however, is a player's team: they can have the best manager in the universe, but it all are down to the player's mentality. They are a wildcard at best. How they will handle Colombia is entirely up to them and little with Southgate's plan.
Colombia was caught on hasty defense by the lucky Japanese at early minutes, and one of their defender have to commit a handball to safe the goal. He was shown a red card. Going against 10 men proved to be quite difficult for Japan, who couldn't convert their numerous chances into goals. They couldn't win against full powered big team like this. Their only scenario to win is to park the bus (their defenders and goalie are good enough to stall even Belgium I suppose), and get a plucky counter attack dash that somehow is able to defeat the still solid Courtois, which is unlikely given how Osako, Honda, and friends love to fumble chances.
Can Argentina still win? I don't know, they are definitely solid. But their guns are small and reluctant, just like a Tiger tank with the 88 mm cannon deleted, and retain only its MG34. The Tiger is solid, but it will less likely kill anyone, because the enemy know its imposing presence, yet it can only do little with the 7.92 machine gun to harm them.
The only reliable team in this tourney so far is Croatia. They are just like the 1998 Boban-Suker era Croatia, only to be stopped by a lucky French defender who scored twice. This Modric-Mandzukic Croatia could be destined to be the champion as well if we took the irrelevant team history and prestige out of the equation.