Tomiyasu was born in Fukuoka on November 5, 1998. He joined J2 League club Avispa Fukuoka from their youth team in 2015. Although Avispa was promoted to J1 League in 2016, Avispa was relegated to J2 in a year. He played many matches as center back from 2017. In January 2018, he moved to Belgian First Division A club Sint-Truidense. In July 2019, he moved to Italian Serie A club Bologna.