Ron,
Fujishiro's says that Naotsugu refers to Mishina Naomichi - this is in fact Naomichi Mishina (1716) where it is stated that he was called Naotsugu. This is the nidai Naomichi and not Kanemichi who signed Naomichi early in his career. The 1681 on this unfamiliar origami seems to be ok if the general working time was 1716 and he signed Naotsugu in his (very) early career. Kanemichi shodai, who also signed Naomichi in his early days, is list 1648 which is too early to be your Tenwa guy. Also see nihontocraft.com:
Naomichi, 3rd generation, 1716, Settsu, Settsu ju Naomichi 摂州住直道, Oite Banshu Mishina Tango (no) Kami Fujiwara Naomichi 於播州 三品 丹後守藤原直道. Son of the nidai Tango (no) Kami Kanemichi, early name Naotsugu 直次. Lived in Osaka of Setsu and moved to Banshu. Worked in similar styles as his father.