Feyenoord striker Ayase Ueda scored a hat-trick as the hosts shrugged off the absence of injured Brighton winger Kaoru Mitoma in Osaka. Daichi Kamada and Ritsu Doan also got on the scoresheet as Japan took their goal tally to 29 in their last seven games - all of which they have won.
But Moriyasu was far from satisfied as he tries to plot a route to the 2026 World Cup in the United States, Canada and Mexico, starting with their next qualifier against Syria in Saudi Arabia on Tuesday.
"We had chances to score more goals. We have to be able to create more opportunities and reduce the amount of times we find ourselves in difficulty," said the coach.
Japan hammered Myanmar 10-0 the last time they had met, in qualifying for the 2022 World Cup.