Mitoma went on as a half-time substitute for Japan as they beat Scotland 1-0 in a low-key friendly at Hampden Park.
He was a threat to the Scots and went close to making the breakthrough.
The Seagulls winger also played a part in a slick multi-player move which led to Junya Ito’s late winner.
Kaoru Mitoma swaps shirts with Billy Gilmour (Image: BBC)
Mitoma swapped shirts at full-time with his former Albion colleague Billy Gilmour, who had come on as a ate sub for the Scots.
Japan now prepare to play England at Wembley on Tuesday.
Albion are likely to be delighted both with Mitoma’s form and fitness and with the workload he was given
Meanwhile Jack Hinshelwood saw his latest international venture cut short.
The Albion midfielder was not involved in the disappointing 1-1 draw with Andorra in a Euros qualifier.
Head coach Lee Carsley later said he had left the squad through injury but did not expand.
James Beadle, the Albion goalkeeper on loan to Birmingham, kept goal for England.
In senior action, Bart Verbruggen played the full game and Jan Paul van Hecke 82 minutes as the Netherlands beat Norway 2-1 in a friendly.
Pascal Gross was on the bench for Germany away to Switzerland and went on for the final ten minutes, during which time his side scored the winner in a 4-3 success.
The German under-21s won 3-0 at home to Northern Ireland in a Euros qualifier as Brajan Gruda started alongside Cologne prospect Said El-Mala, who is understood to be a transfer target for Albion.
That result kept the pressure on group leaders Greece, for whom Charalampos Kostoulas started in a 5-0 win over Malta.