FYI, number in Goroawase reading for 2-9 theory:
1: ichi, i, hitotsu, hito, hi, bi, pi, fi, wan, a
2: ni, ji, futatsu, futa, fu, bu, pu, nu, ne, tsu, zu, ju, nyu
3: san, zan, sa, za, mitsu, mi, ta, da, so, zo, suri
4: shi, ji, su, zu, yotsu, yon, yo, fo
5: go, ko, itsutsu, itsu, i, u, ka, ga...