Takumi Minamino scored two goals as Japan came from behind to beat Vietnam 4-2 in the Asian Cup on Sunday.
The tournament favourite trailed 2-1 in the first half despite Minamino opening the scoring after 11 minutes of the Group D match.
Nguyen Dnh Bac evened the score at Al Thumama Stadium five minutes later and Vietnam, ranked 94th by FIFA, went ahead through Pham Tuan Hai's goal in the 33rd.
Record four-time Asian Cup winner Japan is ranked 17th by FIFA and is tipped to regain the trophy it last won in 2011.
It recovered from the surprise of going behind when former Liverpool player Minamino, who is now at Monaco, equalized in the 45th.
Keito Nakamura made it 3-2 in first-half stoppage time and substitute Ayase Ueda extended Japan's lead in the 85th.
Indonesia plays Iraq in the other Group D game on Sunday.