In my opinion, I think the most important borrowed idea was the Chinese language. Shotoku used many ideas from the Chinese, but I think that this is more important. The reason why I think this is important is because I think that everyone needs communication. The Japanese didn't have their own language back then, so they used the Chinese language to read, speak, and write. Also, the Japanese were very inspired by the Chinese ways of life. especially Prince Shotoku. China is a very well-known country, even back then. Japanese started as a small country, but gradually increased, thanks to the Chinese. I'm not saying that China was responsible for Japan, but it was one of the big major things that helped Japan grow.
Japan and China are not the same as today, but they had very different effects on one another. Even though they are alike, does not mean that they're different. Sure, they borrowed the Chinese language, but because of that they were able to be inspired enough to create their own language.