19-year-old Wague fired Senegal back in front
Moussa Wague may be just 19 years of age but the right-back already has a World Cup after firing home inside the box to give Senegal a 2-1 lead over Japan.
The first half saw the two Goup H sides exchange blows, with Takashi Inui cancelling out Sadio Mane's opener.
After the break, things remained tight with chances for both teams but it would be Senegal who would find the breakthrough in the 70th minute.
Youssouf Sabaly's low cross was met by Wague, who walloped his shot into the roof of the net from a different angle.