Shu Matsuda is known as his best disciple. Matsuena even produced an animated CM to promote his disciple's debut work. Their art styles are almost the same.
His publisher romanizes his given name as Syun, while Matsuena himself tends to use Shun most of the time.
He voiced the robot in Waza no Tabibito.
The composer Tenmon was his senior in high school.
The year of his birth is unknown, but he has stated that he was 19 years old when The Gate to Valhalla was published.