Newbie here!

I bought a used Sekai 2005-2006 in a garage sale for $20 that has served me well for at least 8 years. I lent it to a friend that really needed it for 2 years. It has been seating in my garage for the last 3 years, and I'm seriously thinking about a frame renovation. While I'm debating if the emotional value would be worth the cost, I wanted your help to identify it's model.

It's an all-black Sekai, 61' frame. And it still has a very smooth ride.

I still can identify the following original components:
Suntour VGT Luxe Rear Derailleur
SunTour Spirt Front Derailleur
Suntour Shifters on downtube
Suntour Perfect 6-speed Freewheel
Sugino Bottom Bracket
Sugino Crankset
SR stem
SR Road Champion Handlebars
SR seat post

Serial number: Y0G7752

The paint was in terrible shape when I bought it, and there were no decals left in it besides the front badge. According to this thread, it should be 1980 model built by Yamaguchi. I would appreciate any help you can give me in finding the model.