inshun is actually a famous martial artist , perfectly reasonable for author to choose him as one of the top 16 of japan around that time
you saying this means you clearly didn't read this manga then, since this manga hasn't shown any connection between them (just like in history
https://en.m.wikipedia.org/wiki/Hōzōin_Inshun
“In Japanese folklore, he (and Hōzōin-ryū school itself) is known the most for a legendary duel with
Miyamoto Musashi, who came to Kōfuku-ji to fight with a member of the school. This portrayal of Inshun as Musashi's rival and of the duel appear in many modern popular media, such as the manga
Vagabond, or games like
Ryū ga Gotoku Kenzan!, and originate in
Eiji Yoshikawa's novel
Musashi. However, when historical Musashi visited Kofuku-Ji, Inei was 84 years old and Inshun 16.
[4] Whether due to the old age of the first headmaster of the Hōzōin-ryū or due to the youth of his successor the man who met Musashis challenge was Okuzōin Dōei.
[4] Later on in his life Musashi dueled (and won) with another Hōzōinryū user, Takada Matabee. That took place in Kokura in
Buzen Provincein 1632.
[4]”
This is what I meant by “pop history”
Yea, hey may be Mushashi and Inshun haven’t interacted because even the author felt the Mushashi V Inshun fight is too troupe-y or don’t want to make it so obvious.
With Sasaki surviving and Inshun still alive now and Fuma being the chain-y weapon person. We have all the pieces for another Mushashi legend retelling.
I am just hoping this is not the twist in the end.