Answer:
ハ+西+一 Katakana "Ha" or HACHI, ya(ttsu), ya(tsu), ya, yo - eight / SAE, SEI, nishi - west / ICHI, ITSU, hito(tsu) - one
弱 JAKU, yowa(i), yowa(maru) - weak, make weak
世+木 SEI, SE, yo - world, era / MOKU, BOKU, ki - tree
休 KYUU, yasu(mu) - rest
免 MEN, manuka(reru) - avoid, escape, be exempt from
They all take the "fish" radical (魚 GYO, sakana, uo - fish) to become other characters.
鰌 dojou - loach
鰯 iwashi - pilchard
鰈 karei - flounder
鮴 gori - rockfish
鮸 nibe - croaker fish