Since you are borrowing (either fiat or crypto) to enter a margin position, you will be charge with a daily interest of the borrowed amount. This interest is charged immediately after entering a position. Then at 7:00 AM Tokyo time (UTC+9) the same day onward, it will be deducted from your account for every day the position is kept open.
If the position is taken before 7:00 AM UTC+9, this interest will be collected twice on the first day (once at trade opening, once at 7:00 AM UTC+9). If the position is taken after, interest will be collected once on the first day at trade opening.
You can see this interest being deducted in Accounts & Funds > [fiat/crypto] > Recent Transactions, under the tag Interest Transfer.