It's possible, but as IGH pointed out it may require narrowing and realigning the frame. This is easy-ish to do on an old steel frame like your Sekine. Read on: http://sheldonbrown.com/frame-spacing.html

Many years ago I laced a Bendix coaster brake hub onto a sew-up rim and put that on a Schwinn Paramount track bike. Demented, but it worked and it didn't bend the chainstay.