Hi everyone! I bought an old Sekai at a garage sale years ago, and have ridden it on and off since then (2010). I love the bike, but it's needing some significant cleanup and maintenance soon. I was debating restoring it, doing minimal maintenance to keep it riding, or sell. I'd love to know more about the bike, and if it is considered one of the nicer/important models. The serial number is on two lines:
DS70
514065

Other identifying features are:
SAKAE SX crank
52 tooth large gear marked "SA 307", 42 tooth small gear marked "SA 362"
HTI A19 metal pedals
Shimano front & rear derailurs (12 speed)
Shimano Downtube shifters marked "SL-S434" and "light action SIS"
Joytech rear quick release axle
Sachs front quick release axle
Dia-Compe brakes
Leech brake handles (possibly not original? They're plastic)
Araya wheels, aluminum, 27" x 1.25"
26.3mm diameter seatpost

Pictures are in a Google Photos folder here: photos.app.goo.gl/JvsjSU9qPQcg1XeVA

Any help or pointers would be greatly appreciated, thanks!