Takeda Cavalry "Retainers"

Hi,

Most sources in English indicate that, at least until 1575, each of
the Takeda mounted samurai had two dismounted "retainers." Does
anyone know how the "retainters" were utilized? Did the two follow
directly on the heels of the mounted man, or were they formed in
separate units? Did they wear the typical ashigaru armor or the
better armor typically associated with what one theinks of
a "samurai?" How were they armed?
Thanks