Yes, a KS prefix on a serial number normally indicates Kawamura, who manufactured Nishiki. However, in all my years tracking Nishiki serial numbers, I have never seen one with 10 characters. Invariably, they have been 8 characters and the first number no higher than 3. Kawamura discontinued this serial number format circa 1975 on the Nishiki models.
Based on the presence of a down tube bottle bosses and cables running under the BB, this is much later than early or mid-1970's, though it is definitely entry level. Originally, I was thinking Nishiki's sister brand, Azuki, though I'm having a hard time rationaling why Kawamura would use a serial number format that is so different. Also, this bicycle looks '80s by which time Kawamura had move entry level production to Taiwan.