Amagasaki's first appearance (and only speaking appearance) was in OVA 1, sometime after Tenchi returned to school following the episode involving a mummified Ryoko. Upon seeing Tenchi freak-out briefly upon mentioning a mummy, Amagasaki made the mistake of implying that Tenchi slept with one - and was a victim of one of Tenchi's rare shows of temper.
His next appearance came in a flashback on OVA 3. Amagasaki was moving to Tokyo, and having failed contacting Tenchi on the phone, he made the trip to Tenchi's house, only to discover he was living with five girls! Heartbroken, he relayed his story to Kamikura, with a final message, along with Ikeda - 'So long, traitor!'.
Tenchi in Tokyo
In Tenchi in Tokyo, Amagasaki has a larger role. He was one of Tenchi's friends when his grandfather Katsuhito Masaki sends Tenchi to Tokyo in order to train as a kannushi at a shrine run by a friend of Katsuhito, Dokuzen Tsuchida. He was also one of Tenchi's classmates, along with Dokuzen's grandson and Sakuya.