KanjiJLPT N1
Ripe

mellow, ripen, mature, acquire skill

Mnemonic

You receive a round peach from an old master. He tells you to hold it over flames — only a truly ripe fruit will release its sweet nectar when warmed. The juice drips and sizzles, proving this peach has reached absolute perfection through patience.
Additional thoughts
Picture the round peach glowing over the fire, its skin splitting as fragrant juice hisses on the coals. The act of receiving it from a master ties to the idea of earned mastery — ripeness through time.
Quick recall
Receive a round peach and hold it over flames — only when truly ripe does its nectar flow.

Details

The keyword for 熟 is ripe. This kanji conveys the idea of something being fully matured, cooked thoroughly, or brought to completion. It extends beyond literal ripeness of fruit to encompass the notion of mastery or proficiency gained through long practice, as well as the thorough cooking or heating of food. The underlying concept is that of reaching a state of full development or readiness through a gradual process.
On'yomi
じゅく
Kun'yomi
う.れる