The Japanese have never reached the last eight in their six appearances since making their finals debut in 1998, but came agonisingly close in Russia four years ago.
Goals from Genki Haraguchi and Takashi Inui gave the Samurai Blue a two-goal cushion over heavily fancied Belgium in their last 16 meeting in Rostov-on-Don, putting Japan on the verge of an historic victory.
But their inability to close out the game proved costly, allowing Belgium to claw their way back into contention with two goals in five minutes before Nacer Chadli's injury-time winner capped the most thrilling game of the 2018 finals.
It was a cruel blow that denied Japan their best-ever result on the global stage and it was a loss that threatened to haunt Moriyasu and his team as they prepared for Qatar.
"Not only myself, but the players have carried the pain from Russia for the past four years," he told the Asian Football Confederation's official website prior to the finals.
"If our players can perform to their potential and leave everything on the pitch, I think the results will come. For this to happen, I know I have to manage and take care of the team thoroughly."
Moriyasu showed his tactical nous to defeat the Germans, introducing Arsenal defender Takehiro Tomiyasu at halftime to switch to a back three after seeing his team under constant threat throughout the first half.
The tide eventually turned in Japan's favour and the manner in which Moriyasu used his five substitutes paid off handsomely, with scorers Ritsu Doan and Takuma Asano also coming off the bench to spectacular effect.
Japan next face Costa Rica on Sunday knowing a win will take them a step closer to the knockout rounds, but Moriyasu is unlikely to allow his players to become complacent.
"The first game is very important, but the result of the first game isn't everything," Moriyasu told the AFC.
"We need to focus on each match as it comes and my job is to manage and stabilise the team so it doesn't get affected by each result."
