Well, for starters, Medaka was the one who kicked off this arc, and she still is an important character in their universe. Her presence in this arc (and all previous ones) is justified.
The Demoted to Extra
trope on Medaka's character page should probably be removed, as the trope is meant for minor
characters who become unimportant
to the story. And while it's true that Medaka is getting less screentime, she is still fairly prominent in the story. She's not an extra. At least, not yet.
And about Zenkichi... his almost zero presence in this arc is also justified, given that he's not as smart as Akune and Kikuchi, nor as opportunistic as Kikaijima and Kumagawa. From the start I've already predicted that Zenkichi won't be showing up much in this arc.
So basically, I think it's just you missing Zenkichi. His absence is not particularly conspicuous given that previous events give plausible reasons for it.
edited 13th Sep '11 6:51:31 AM by fillerdude