Transferring money to buy a house

Hey all. I apologize if this isn’t the right forum for this question. My family and I are considering buying a house in Japan, and I might need to transfer funds from the U.S. to cover some of the mortgage costs. I’m wondering if there’s a preferred way to transfer funds to Japan that minimizes tax liabilities. I’m currently exploring options, but I can either borrow from my 401k, try to ask my family for a loan, or exhaust my savings account. I’m not sure if the tax implications will be the same regardless of the method, but I’d appreciate any insights or experiences anyone has with this. Btw I’m a U.S. citizen and my wife is Japanese. Arigato Gozaimasu.

by CGekko