I need help with this "Signature"

[DKR]

Hello,

 

I need some help.

This the nakago of a little tanto. 

In my opinion, a work from the Muromachi period.

 

I can read the first three characters : Bishu Osa (fune ?) .......then that was it.
No idea what the other characters  might mean.

 

Does anyone have any idea what the remaining characters should mean ?

Edited October 3, 2021 by DKR
Typo

[kyushukairu]

Didier, I would say that the location is Bishū rather than Bichū, and would hazard a guess at the smith being Sukemune (備州長船祐宗)

[DKR]

Oops, ....the typo is my fault. 

Thank you .   

 

Sukemune ..... OK,  thanks for your help. 

 

Maybe someone else  with a different idea ?