I'm torn on Serizawa/Hikari issue. Are they one and the same? Or are they separated beings? I put them on the poll here as being the same character, mostly to avoid confusion, but I really am not sure if they really are.
Sometimes, I wish Hikari would simply assume Serizawa's form so I don't have to agonize over the subject. But if that is the case then, there would be no meaningful scenes of Ryuu and Serizawa besides those shown in the flashback. There would also be no intense confrontation between Ryuu and Serizawa (who was still Tsurugi and didn't remember being Serizawa). Not to mention that Serizawa would certainly not be alive/survive had Hikari not merged with him.
I'm not really sure what my point here is. All I know for certain is that Tsuburaya had never defined any clear-cut rule regarding the relationship between an Ultra and his human host. The line is even sometimes blurred within the same series, let alone across different Ultra series.
(Oh, and I may have said this somewhere already, but I have a special fondness for the Ultras who make their own human forms (not that I don't like the ones who do use human hosts, Tsuburaya's inconsistency on the subject notwithstanding). For me, there is some certain morbid enjoyment in seeing these Ultras, who have no true understanding of human knowledge to guide them, display their awkwardness, in following their fish-out-of-the-water experiences here on this planet called earth where they can never truly be the same as the natives no matter how much they try to fashion their outward appearances and mannerisms to fit in. Seriously, it's a disaster waiting to happen when they eventually and inevitably commit some mishaps. (Wish I have some specific examples, but my knowledge on these "non-hosted" Ultras is woefully lacking. My head is even too much a blank at the moment to attempt to come up with some (usually) amusing incidents caused by misunderstanding or misinterpretation on Mebius' part.))
EDIT: Thanks for interesting discussion(s). :)