As Nagagi is worn by wrapping the right side over the body and then the left side overlaps it, the right side comes back over the left side--This is called Migimae or Ujin as stated above.
和服を着るときに右前、つまり右衽（うじん）に着るので、右の衽のほうが左の衽よりも空間的に後ろに位置することになる。