[Kiwami]

Yup, some Ultras have human hosts, a trope started with the original Ultraman and continued with Z, some others, like Ultraseven, assume a human disguise.

Then there are other cases like Orb who was once a normal mortal but "granted" the powers of Ultraman through the light. So he himself becomes an Ultraman.

Riku is similar to Orb, but has a different origin: He’s an altered clone of another Ultraman (I won’t spoil who since you seem unaware) but he grew up as a human and can assume an Ultraman form as well. Although Riku seems to need fusion material as his own Ultraman form is either not available to him or he hasn’t figured out to use it yet. You can see what would be his "original" form before the other Ultras join into him in this very episode.

It’s interesting reading your thoughts by the way. Ultraman is always a bit more reliant on what came before, as apparent through the non-ending reuse of the “past Ultraman as transformation items”-trope, but some shows manage it better than others.

Z as a (self proclaimed) pupil of Zero brings his entire mythos into the fray, of which Geed is a big part of. Maybe you’ll get interested enough to check some of it out one day, Ultraman Geed is a fantastic show.