Hajime Moriyasu's side opened the tournament with an unconvincing 3-2 win over Turkmenistan in Group F.
Striker Yuya Osako, who scored two goals in that game, will miss the Oman match due to injury.
Japan are the most successful side in AFC Asian Cup history with four titles.
But the 'Samurai Blue' suffered a shock quarter-final exit to the United Arab Emirates in Australia 2015.
The result against Turkmenistan will do little to persuade fans that Japan have found their rhythm under Moriyasu - who took over from Akira Nishino after the 2018 World Cup.
However a strong performance against Oman, coupled with progression from Group F, will quickly change that outlook.