Hey Ji Ho Yoo,
I think this is what you're looking for:
Admin > Settings > Checkout > Order Processing
... and then go to your Admin > Settings > Payment Providers > Payment Authorization
Setting it up like this will allow your store to automatically capture the payment, and then automatically fulfill only the Gift Cards in an order. Capturing payment automatically is pretty standard. If you don't want to go through with the order, then you can just cancel it (which will prompt a full refund) -- and there are no penalties for cancelling/refunding an order.
Hope this helps! :)
In fact, payments are only captured after gift cards are being redeemed. This is a law that was put in to place to protect the consumer. Moreover, after going through similar issues with my store, I decided to outsource this type of thing. I found a company that specializes in everything gift cards. Rise.ai was able to take care of all my gift card needs. It was a very easy solution to my issue and I would strongly recommend it.
I hope this helps!