Need Help Identifying this sword please.

[NinjaBear]

The topic of identification seems to be a really uphill struggle. I don't have the level of knowledge as some of you guys and you have been super helpful in the past which has been very appreciated. 
I work for a pawn shop, and in a passing conversation with one of my customers, he mentioned he had a sword. I love these things, and we hardly ever see real katanas. So I said if he ever felt like bringing it by for me to see, I'd love to see it just for my own interest in seeing a piece of history. 

He brought it by and was kind enough to let me take it apart to inspect to see if it had the swordsmiths name on the tang. And it did! I also thought it was interesting that the serial number was 9. 
But besides my own personal curiosity and interest, I couldn't share any other details with him about it. He says his father brought it home in WWII. 
I told him I would post here to see if I could learn anything about it to share with him. I'd love some help!
 

[NinjaBear]

Here are some pictures of the guard as well.

[John C]

Anthony:

Just to get the ball rolling, I can't speak to the blade but the fittings are from a WWII Naval sword (i.e. kai gunto).

 

John C.

[Conway S]

Anthony, 

 

I believe the signature is Yoshikuni, and the first two characters (top-bottom) might be E-Saka. 江坂義國. The sword looks to be of wartime manufacture. It’s in nice shape overall with higher quality fittings.
 

Conway 
 

 

[mecox]

Anthony,  looks to be YOSHIKUNI 義国: real name Esaka Masao (江坂正男).
Born Meiji 33 (1900) May 26. Reg. Showa 17 (1942) August 24 (age 42). (“Esaka Yoshikuni” SEKI)    He lived in Gifu, Kamo-gun, Tomita-mura.    [Slough p.197]

 

[Brian]

Not a serial number, but assembly numbers to keep all the parts together. No relevance to where it was made in the timeline. But nice if all parts are matching numbers.