Ultraman Nexus was the 2004 Ultraman series, which feature (generally)
young people who have the ability to change into giant form to fight
monsters. I have it listed on the main page because this is the only
Ultra series I've seen.
Dogged Persistence: Ren is persistent. Spoilers for last half of
Complete / Gen / Warnings: None
Characters: Senjyu Ren
Main fandoms page