665. What characters can be added here so that each character contains a part of the previous character? 動 -> _ -> _ -> 坂

Answer:

動 -> 加 -> 吐 -> 坂

動  DOU , ugo(ku) - move

加  KA, kuwa(eru), kuwa(waru) - add, append, join, take part

吐  TOU, ha(ku) - spew, vomit, give vent to

坂  HAN, saka - slope, hill