The words “plan” and “scheme” are similar. Kinda.
The word plan isn’t difficult to understand when it means to prepare or a preparation. It can both be a noun or a verb, and translates most simply to 준비 in Korean. In Korean also, 준비 is the root of either a noun or a verb. In English and in Korean, the word is basic and simple.
“Scheme” Has A Slightly Different Meaning in British English
When someone has a specific plan to save money in a fund, or a bank, with a plan to withdraw that money at a later date, that is frequently called a scheme. A scheme would, in that case would be very similar to the word plan. The British would not consider it to be anything which may be illegal or one party taking advantage of another.