Answer:
They all have a reading that is the same backwards.
一 ICHI, ITSU, hito(tsu) - one
何 KA, nan, nani - what, which, how many
鮮 SEN, aza(yaka) - fresh, vivid, clear, brilliant
粗 SOU, ara(i) - coarse, rough
怪 KAI, aya(shii), aya(shimu) - dubious, suspicious, strange