こう is one of the most common on’yomi in Japanese. A quick check of a joyo kanji list suggests it is the most common joyo on’yomi reading, with 60 kanji in total (beating out しょう at 57 and し at 49).
Currently, WaniKani uses “Kouichi” as a reading mnemonic for quite a lot of these kanji. Sometimes, this works well; こう is used as a reading for quite a few kanji involving authority figures, which works well if you look up (仰) to Kouichi as WaniKani’s emperor (皇). Besides, we like (好) Kouichi, and wish him happiness (幸). We’re glad he constructed (工) this school (校), and will be sure to renew (更) our subscriptions (購読) until we’ve become adept (巧) and burnt all our turtle shells (甲).
However, filial piety (孝) aside, it can be a bit confusing (慌) to constantly (恒) with such a broad (広) mix (交) of characteristics. A lot of the time, they make sense after (後) the fact, but actually going (行) from hither to yonder (向) is a much taller (高) order; like going towards a harbor (港) without a light (光) to navigate (航).
I think (考) that perhaps some こう readings could be more effectively (効) remembered using “core” as a mnemonic, particularly when the meaning involves some sort of descent (降). I’ve drafted (稿) up a few examples, which I will here make public (公):
孔 (cavity)
Meaning (mostly unchanged):
You see a child with an umbrella in front of you. Suddenly, they fall straight down into a cavity in the road. It’s a big hole!
You run over to where the child fell. Staring into the cavity, you see the child using their umbrella as a parachute. Perhaps they’ll reach the bottom of the cavity unharmed?
Reading
Unfortunately, this cavity leads all the way down to the core (こう). Umbrella or no, that kid is doomed.
*Picture the child with their umbrella, slowly drifting down the cavity. It takes hours, but they still hold on for dear life,
坑 (pぴt)
Meaning (unchanged):
In the dirt, you find a lid under the table. You lift it to reveal a deep pit. Why is there a hole under your table?
You pull away the lid and crawl inside. There is a ladder that takes you deep into the pit.
Reading:
This pit goes all the way down to the core (こう).
候 (climate)
Meaning (unchanged)
A leader with a stick, a hook, and an arrow is able to change the climate and weather. Not just the type of climate that causes sunny and rainy days though, the political climate too, because they’re a political candidate too.
Reading
The candidate wants to save the climate by freezing the Earth’s core (こう). It’s his core policy proposal.
Who is this candidate? Why, none other than emperor こうichi! Kouichi cares about the climate so much, he decided to run for public office!
降 descend
Meaning (unchanged):
Inside the building is the Winter Cow. You need to see it, so you go inside. It is deep down in there, and you’ll have to descend to reach it.
Focus on descending the stairs. There are many signs that say “To Winter Cow: descend” with an arrow pointing down. “I guess I’ll have to descend,” you say.
Reading:
The stairs go on and on. “How far must I descend!?” you yell. “To the core (こう)!” a voice responds. “You must descend to the core!”
肯 agreement
Meaning (unchanged):
We must stop the moon. That, at least, we can come to an agreement on.
There are a group of people pointing at pictures of the moon coming closer to earth. They are the world’s leaders, and although they don’t get along normally, this new attack from the moon has united them in agreement: we must stop the moon.
Reading:
You agree that the best way to stop the moon is to blow up its core (こう). You’ve all seen Armageddon, so you all agree that it will work.
Emperor Kouichi hums the tune to I Don’t Wanna Miss A Thing as he signs the agreement.