Japanese count big money in units of 10,000. They don't for instance, have a word for 'million.' -- a million is actually called 100万. Which would be logical if it were written with 万-sized commas： 100,0000 . . . but it's written with rest-of-the-planet commas, like this: 1,000,000. I'm sure some asshole thought he was doing the rest of the world a favor with this compromise, but actually that just makes it more confusing for everyone. Probably it was the same motherless douche who decided to import all the on-yomi from China and get them all wrong.
You can think of this as the katakana KU (ク) plus the number one over it.
A MAN touches your KUchie with ONE finger. ten thousand times!!
just in case
万 (10000) + 一 (one)
= 万が一 (just in case)
just in case (literally, 'on the one-in-10,000 chance that something goes wrong')
万 (10000) + 歳 (years old)
= 万歳 (banzai!)
Fuckin' banzai, man!!!! (literally '10,000 years', meaning, 'May the Emperor live 10,000 years!' is what you shout as you charge into battle)
万 (10000) + 引 (pull)
= 万引き (shoplift.)
||direction / method / person
||EVEN ON TOP
方 means 'person', so naturally it has a little 'head' stiking up on top - you can think of that as the person's beret!
万 is a number, so naturally it has NO HEAD. It's EVEN on top - which makes sense because 10,000 is an even number.