[Mesnick]

Since the question of a quaternary rider has come up, what do you think defines this type? Besides the fact that he appears fourth (but not always) and gets less screen time than the main trio, but more extra riders? That is, the classic (of course, there are exceptions, the franchise is over 50 years old) the main rider is an optimistic good guy, the secondary one is a conflicted lover to fight; the tertiary suffers the most. What does the quaternary have?
I also think we need to highlight the last rider. It's the goodie (because final boss riders are more or less justified) who becomes a rider so close to the end of the show that he's practically useless. Tsukuyomi and Juuga are the most obvious representatives, but I think there will be a lot of them in the future.