Welcome aboard! I don't know how much more you're going to find on it. A lot of the Japanese manufacturers made machines for anyone who bought enough to put their name on them.
That's the bad news. The good news is there are probably a whole bunch of similar machines out there with slightly different outer parts but the same insides. There's a very good chance Singer Class 15 bobbins and standard needles will fit. It looks like a pretty decent machine from the late 60s or early 70s to me. Do you have the piece that fits on the front for when you don't need the free arm? Be very happy you have the manual. Even if it is basic it beats not having one.
Sorry I'm not more helpful,
Rodney