Noriaki Kumagai, born March 18, 1970, in Sapporo, Hokkaido, is a Berklee College of Music graduate who replaced Masaaki Hiyama as Casiopea's drummer in 1993, remaining active with the group through 1996. He kept a looser connection to Casiopea afterward, appearing on later live and anniversary releases through at least 2009 and again in a 2016 lineup.

After leaving Casiopea's main lineup, he became a first-call session drummer for artists affiliated with Being, one of Japan's major record label groups. His lasting creative home, though, has been the fusion band Trix, described in secondary sources as a "power fusion combo" drawing members from both Casiopea and T-Square. Trix has released a new album in nearly every year from 2004 (Index) through 2023 (Parade), an unusually consistent output for a working fusion group. He also recorded on two solo albums by Casiopea founding guitarist Issei Noro, Under the Sky (2001) and Light Up (2002).

He has no leader-billed albums under his own name; his recorded identity outside session work runs entirely through Casiopea and Trix as a band member.

Kumagai's playing sits in the power-fusion tradition shared by Casiopea and T-Square — the two bands Trix draws from — combining technical precision with the driving energy characteristic of Japanese jazz-fusion's commercial peak era and its long afterlife in working bands like Trix.