Is there a reason Shinjo Outriders have a Yumi but no arrows?
Shinjo Outrider
Most likely an oversight.
They're supposed to borrow them from the Akodo who has a bow and arrows but no Ranged skill.
On a related note, given that a quiver is functionally unlimited arrows, is there a reason (there might be, I guess) why the Ninja only gets 10, rather than his own quiver?