610. This #kanjipuzzle is about evolution. Start with one character, add a few strokes, and get another, then repeat. 一 -> ? -> ? -> ? -> 語

Answer:

一  ICHI, ITSU, hito(tsu) - one

二  NI, futa(tsu), futa - two

三  SAN, mi(tsu), mi(ttsu), mi - three

言  GEN, GON, i(u), koto - say, speech

語  GO, kata(ru) - story, tell