The subject bicycle appears to be a Sekine RM-30 from the very early 1980s. It is an upper, entry level model. The frame is hi-tensile steel and the rims are steel. The brakes appear to be Shimano Tourney, while the crankset appears to be a Shimano Selecta T. The derailleurs are a bit harder to identify, either Tourney or Altus ST but the shift levers look like Altus. During this era, it was rare to get aluminum rims on hubs with nutted axles.