In addition to having world-class bike infrastructure, South Korea is an excellent travel and transportation hub to other nearby countries. From a bike touring perspective, it’s very economical and convenient. Simply ride across Korea on all bike paths down to Busan City. Take a very good ferry over to Japan for W120,000-W200,000 return depending on the season. From Japan or Korea, you can get cheap flights to Taiwan.
This would make an excellent multi-country bike tour. All three a VERY bike friendly. Korea wins for being able to ride without cars on the cross country bike paths, for ease of camping, many cheap motels and sleepover spas, etc. A great holiday on a bike.