How can I persuade my father who boycotted Japan to allow me to travel to Japan?

It's very simple. First of all, you promised your friend to go to Japan. It is dishonest not to attend an appointment to visit Japan. Do you want to be a dishonest person? What Confucius said went in one ear and out the other. Then, it's no big deal to visit Japan. Is it treason to visit Japan once? So those Japanese scholars in China and those martyrs who came back from studying in Japan, such as Lu Xun, are traitors? So don't be afraid, the world is so big, you need to see it, and you promised your friends that you can't change it, you must go. Now many adults are very dissatisfied with Japan. When it comes to Sino-Japanese relations, it will involve the Nanjing Massacre and so on. It is normal to understand your parents and go to Japan at the same time. Although Sino-Japanese relations are not very good politically, they are definitely first-class allies in culture, and the culture of that country is highly recognized by China on earth.