In 1986, comic creators John Byrne and Marv Wolfman collaborated on a wholesale revision of Superman, re-origining the character in many ways. In his intro comic, Byrne mentioned how going forward, the stories could no longer feature such random scenes as the one he cited. In a 60's story, on his way to do something, Superman was flying over the ocean when he ran into trouble from a sea serpent that he overcame, without the serpent being the focus of the story or related to the enemy he was fighting. It just showed up, was there, gave him trouble, then went away.
I mention this because, while I obviously love this series, it has a lot of sea serpent motives and plots and things that never seem to begin, take root, or really conclude. I am very hard on the stuff I like, and I look and see things like who Unknown Man might have been to have such free run of the DRI, what trouble Yuka's Mom caused for Nana, if any, and where the other cast members were in the finale, and it makes defending the series harder. Why did Mayu's stepfather never come after her again? Why did Wanta's supposed former owner not show up, making accusations? Did Young Lucy ever go out of the Kamakura area after the train ride? What prior cred did Chief Kakuzawa have, to be placed in charge of such a project and have such an immense facility built with such free rein? When Maple House was invaded, did any of the neighbors get upset, what with crashed helicopters in the area?
Byrne concluded his comments by saying they'd never get away in the present with the serpent just showing up. It would have to be encountered for a reason relevant to the plot, find out where it came from, and tell us how it was dealt with in some way after it was overcome. In any fandom, a fanboy like me is gonna nitpick, no avolding that. But I think if Okamoto-San had dealt more with these types of questions, the series would have been a lot stronger overall.