Aso was a New Zealand Schools representative in 2012 and later went on to be a member of the New Zealand Under-20 sides which competed in the 2014 IRB Junior World Championship and 2015 World Rugby Under 20 Championship. After finishing 3rd in the 2014 edition, Aso's stunning solo effort helped propel them to a 21-16 victory over England in the final of the 2015 tournament which was held in Italy.