The Hitachi mark does mean it was cast there, but that's not the "brand". I think it's an Eisho shell, and they used Hitachi as their casting partner. Takahashi also made shells and crowns with the Hitachi mark.
The lugs are either Eisho Royal or a very good knock-off — I'm betting they are real Eisho lugs. Which is a good thing, they are terrific, super well made and aesthetically pleasing (to me). They're popular with high-end Japanese FBs, especially Keirin. You could get them in other countries though, so this doesn't narrow it down. I made maybe a half-dozen custom frames with those lugs.
I slightly preferred the Takahashi shell (also cast by Hitachi as I said) but my reasons are not important — the Eisho shell is awesome, way nicer than a Cinelli IMHO. The castings you can buy nowadays are mostly crap by comparison. I don't mean they break or anything practical like that, I just mean the curves aren't as pleasing and the surface finish is rougher. You have to hold the raw shell or lugs in your hands to appreciate how finely-made they were. Or maybe still are, if they're still made? I haven't been able to find any to buy for quite some time, but no doubt there are stashes of them in some better Keirin framebuilders' ateliers. Since I'm not currently building frames, I haven't been looking too hard.
Mark B in Seattle