2429. Why do these five characters all seem so reflective? 甲 丙 宇 宙 輩

They all look the same when reflected in a mirror!  

甲  KOU, KAN - first in a series, high voice

丙  HEI - third in series

宇  U - heaven

宙  CHUU - midair, space, heaven

輩  HAI - fellow, colleague, companion