Nonaka entered the House of Representatives through the Kyoto 2nd district by-election of 1983, in which two seats were open following the death of incumbent representatives Shigesaburo Maeo and Sen'ichi Tanigaki.
Nonaka menjadi anggota Dewan Perwakilan Rakyat dari distrik Kyoto 2 lewat pemilihan pada tahun 1983, di mana dua kursi tersedia setelah kematian anggota parlemen petahana Shigesaburo Maeo dan Sen'ichi Tanigaki.