[Suzu]

Quote:

Originally Posted by Matrixbeast

You know, considering Riders, couldn't we technically count any of the Ace monsters from Blade?
Mild spoiler warning, but Chalice's "Rider" form is just the Mantis Undead wearing a buckle, as he doesn't transform into a Rider, but takes on the appearance of the Undead's card he scans through the Chalice Rouser.

Technically, yeah. If any Undead Hajime transforms into is counted as a rider, then even his human form would be a Rider. Or you could say Hajime isn't even a rider, if you only consider those with a man-made belt a rider (which makes Kenzaki lose his rider status at the end of the show).
I think the show goes just with the fact that Mantis Undead looks like a rider (due to the design) and is Hajimes default battle form.