Answer:
They all have a reading that is the same backwards.
雨 U, ame - rain
弟 DAI, TEI, otouto - younger brother
卸 oro(su) - wholesale
浴 YOKU, a(biru), a(biseru) - bathe, pour over, shower
甘 KAN, ama(i), ama(eru), ama(yakasu) - sweet, indulgent, coax, optimistic