I Have an Arbitrary Door, Go Back in Time and Make the Difference

A young man in the 21st century who has been involved in the war has been given a door that allows him to go back to the past and see how he bought gold antiques in the past, resold them to make a profit in the real world, and spent a lot of time in the real world, inviting friends to drinks and dancing when he had nothing to do. If something happens, go back to the past and continue to work hard to make money! There is no problem in this world that money cannot solve. If there is, it is because the money given is not enough. This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.