The tubing is Ishiwata 022, similar in gauge profile to Columbus SL. 022 was most notably used for Bridgestone's MB-1, particularly in later years of the Petersen era.

The frame is probably at the higher end of Maruishi's catalog, although the brand itself doesn't have a tremendous amount of panache in comparison to some other brands in that era (Panasonic).

I'd fix it.