Hi - i know relatively little about bikes and cycling. I've inherited this bike, bought 2nd hand in early '90s. Riding it regularly and enjoying it. I'd really like to know what it is!

On the frame it says "gemini" and "sports delux" (this is probably just marketing stuff), a gemini logo (picture of which is below), a sticker telling me its tange 900 cr-mo double butted steel.

Components are shimano. Front sprockets are 52/40. Rear are 14/??. Derailleurs, (DT) shifters, brakes etc. all say 'shimano', with no distinctive badging. Rear derailleur says 'light action'. Bars have a 'ct' logo and 'sakae japan' inscribed. Crank arms (things connecting pedals to frame, i think that's what they're called ) say sakae SA.
Wheels (probably original) say 'ukai 700x25c japan'
Seat says 'vento propizio' on the side (i'm guessing not original, as rest of bike appears to be japanese)

From my internet sleuthing i guess its from late '80s, but not sure
anyone with any ideas, you're a genius! please post
Thanks very much!