|This article is a stub. You can help Aikatsu Stars! Wikia by expanding it.|
Yamaguchi (山口) is the director of S4's special programs. He later attends Yume's first solo concert.
He is very serious about is work and acts kind to those around him.
- He bears a resemblance to Shou from Pretty Rhythm Aurora Dream.
- He shares his seiyuu with Axel from OZMAFIA.