He was born in Takamatsu, then in Ehime Prefecture but now in Kagawa Prefecture, as the first son of Komon Miki, an antiques dealer.
Miki was admitted into Tokyo Vocational School, called Waseda University from 1902 and on, where he counted among his classmates future politicians Ryutaro Nagai and Ikuo Oyama and baseball player Shin Hashido.