Prepayment fee, prorated by remaining period
Repaying a loan early triggers a prepayment fee, usually charged only within a fee period (e.g. 3 years) and shrinking over time.
Fee = principal × rate × (remaining days ÷ fee period). For example, repaying 50M KRW at 1.2% one year into a 3-year period applies the 2/3 remaining ratio, giving about 400,000 KRW.
After the fee period ends, there is no fee. Rates and periods vary by product (mortgages are typically 1.2% over 3 years) — check your contract. See the DSR & loan limit or loan calculator.