Look at me resurrecting an ancient thread...
From 45 years before Kairyu Daikessen, the hero Jiraiya was showing up in a bunch of silent films. One that still exists in fragments is Goketsu Jiraiya (1921).
I've watched this thing at least 4 times in the past day or so and despairing from the fact that there seems to be no PD version of it with sound, .
I don't know if it's the FIRST but certainly an extremely early tokusatsu film, including suitmation. Director Shozo Makino uses locked down cameras and all of the action is very stylized in a sort of fusion of Kabuki and Bunraku. Very reminiscent of Melies better shorts.