After reread this masterpiece I just discover that in that missing poster wasn't written "parents " just" guardian " so maybe Nabi is orphan. Also their age is "about" and fact that Nabi wasn't really afraid of other people and new place after come to devil kingdom maybe because they was at orphanage from the start so they somehow used to change of people and scenery
This chapter was truly a masterpiece (づ ̄ ³ ̄)づヾ(☆▽☆)