RYUJIN (formerly known as GYZE is a metal band originated in Hokkaido, Japan. Coming from the very north of Japan the members of the band label themselves as "Northern Nostalgic Metal band".

The metal trio consists of Ryoji Shinomoto (guitar/vocals/composer), Shuji Shinomoto (drums) and Aruta Watanabe (bass/vocals). In early 2019 the band announced a new guitarist, SHINKAI, to be joining the band, while the drummer Shuji temporarily stopped his activities in the band, being substituted by a session drummer Han-nya.

Under the name GYZE, they released four full-length albums and three limited edition EPs. A fifth studio album under their new name RYUJIN was announced on 13 September 2023.