Japan pulled off a surprise 2-1 victory over a 10-man Colombia in their Group H opener in Saransk on Tuesday. Here are five things we learned from the match.

Osako is the man up front for Japan

Yuya Osako has proven himself to be Japan's first-choice striker. With Japan rotating between the Werder Bremen forward, Mainz's Yoshinori Muto and Leicester's Shinji Okazaki as the lone target man in their warm-up matches, Osako's 73rd-minute winner showed he was the man for the job. The 28-year-old continually made dangerous runs into the box, held the ball up well, and even backtracked to crucially block a close-range shot by Colombia danger man James Rodriguez.

(Yu da man: Osako (15) celebrates after sealing Japan's famous win) 

Honda still a dead ball master

Keisuke Honda can still deliver a dead ball like few others. The veteran playmaker made an immediate impact for the Samurai Blue after coming on as a 69th-minute substitute, forcing a save with one of his first touches, then delivering the corner which resulted in Osako's winner. The 32-year-old sent his corner from the left side curling and dipping past the Colombia defenders into the path of the flying Osako.

(Blonde bombshell: Honda played a pivotal role in the win after coming on for Shinji Kagawa)

VAR no fix-all for referees

Even in this age of video assisted refereeing, mistakes will still be made and incorrect decisions will still swing matches. Replays of the 37th-minute foul that led to Colombia's goal clearly showed Radamel Falcao initiating contact with Makoto Hasebe before the pair tumbled to the ground. With the incident taking place on the edge of the box, the error was a particularly costly one.

(Hasebe (17) remonstrates with the referee after the dubiously awarded free kick)

Colombia fans are here and they're loud

Colombia have one of the most dedicated (and loudest) groups of traveling fans at the tournament. They turned the Mordovia Arena into a cheering, jeering ocean of yellow, giving the match the atmosphere of a home game for La Tricolor. When Colombia went down to 10 men after just three minutes, their fans grew in voice, seemingly willing their side to overcome the disadvantage.

(The Colombia fans were loud, but ultimately silenced as Osako won it for Japan)

A man down, La Tricolor keep swinging

The Colombians are a tough and aggressive outfit. Even after being reduced to 10 men, they continued to take the attack to Japan, forcing the Samurai Blue defense to soak up pressure for extended periods. Tottenham Hotspur defender Davinson Sanchez in particular made his presence felt, manhandling opposing players as he turned defense into attack.

(Sanchez (23) outmuscles Osako) [Getty/Kyodo]