In my opinion South Korea (on average), is the most advanced due to the fact it is one of the most digitally connected countries, the highest number of industrial robots per capita, largest smartphone manufacturers in Asia etc. However if you take into account the 1st tier cities, China is definitely the most advanced due to the adoption of 5g, Shenzhen with a start-up scene that rivals Silicon Valley. In many ways, China has the most high tech military with the only Asian country to use domestically manufactured 5th generation fighter jets, a nuclear weapons program and use of hypersonic missiles. They also have the largest space program. Japan falls in last place. Don't get me wrong, Japan has its merits such as the Shinkansen, most advanced robotics (Asimo) and managing to land spacecraft on comets. However, there are too many drawbacks such as the use of fax machines, Hankos (Japanese stamps), a heavily cashed based society (both South Korea and China are big into digital payments), use of flip phones and a lot more. However, feel free to discuss and I look forward to hearing your opinions. Honestly, both 3 countries are high tech.