I don't think it is japanese but I am no expert. it looks to be a Randonneur type (sport touring) bike. also it can't be too bad with a 531 frame and fork. I am thinking maybe a raleigh or le june? the front has eyelets which are more for fenders. is it your size? judging from the seat position it is just a bit big for the current rider.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk