It was great to hear you got back in the saddle after some health issues. I can definitely relate to the soreness - my rear wasn't too happy after our ride either!
I'm actually in South Korea at the moment on a trip. A few days ago, my guide Paul, took me on a bike ride to the famous Nami Island. It was beautiful cycling around the leaf-filled pathways and taking in the scenery. Paul was a great guide - he introduced me to this activity and also showed me some other top tourist spots around Korea
https://gowithguide.com/korea We got to see palace districts like Gyeongbokgung and traditional villages like Bukchon. We also tried some local cuisine here.