Ryusei Tendo went to St. Lilith's Academy along with his childhood friend Dina Lancaster. He spent his first 7 years in Japan and the rest with Dina which explains his knowledge of Japanese. He has a goofy personality. He picks on Melanie's height even though he's aware she skipped a few grades. Sometimes, he and Dina would bicker about simple things but it usually gets resolved within a matter of minutes. He also picks on Simon and keeps referring to him as a "she" which had led to misunderstandings in the past.

UPDATE: Ryusei was supposed to be revealed as an Earth angel under Simon and Ethan's noses in the end, but due to a change in the script, it will be revealed that Simon knew Ryusei's true identity. It was decided to keep his true background to the people auditioning a secret but due to the change, his true background will now be told.

Ryusei is an Earth angel who decided to keep an eye on Simon Lilia, the founder and director of St. Lilith's Academy. He decided to attend his school a year prior to the events of the series, with Simon's knowledge. During his attendance at the school, he met Dina Lancaster and took a liking to her. He used his Angelic Ability to create fake memories to trick her into thinking they were childhood best friends.