This is the 13806th most frequent Korean word.
마통
"마통" is slang for "bank account" in Korean.
In this sentence, '마통' refers to a subway card used for travel in cities like Seoul.
나는 서울에 도착하자마자 마통을 열었다.
I opened my subway card as soon as I arrived in Seoul.
Here, '마통' indicates a stored-value transportation card and highlights the necessity of adding balance to it.
그는 마통 잔액이 부족해서 충전해야 했다.
He had to recharge his subway card because the balance was insufficient.
In this context, '마통' represents the physical subway card, and the sentence gives advice on what to do in case of loss.