Answer:
a) 架 -> 林 -> 森 -> 禁
架 KA, ka(keru), ka(karu) - hang, build (a bridge)
林 RIN, hayashi - woods
森 SHIN, mori - forest
禁 KIN - prohibition
b) 柔 -> 棋 -> 期 -> 脚
柔 JUU, NYUU, yawa(rakai) - soft
棋 KI - go, shogi, Japanese chess
期 KI, GO - time, period, term
脚 KYAKU, KYA, ashi - leg