Intact deceased bird observed under building during a visit to Seoul. I contacted the Seoul Wildlife Center and they kindly advised this may be a Leaf Warbler spp. This has been uploaded to the FLAP Global Bird Mapper (Object ID: 1166108). I had some trouble with the page not translating to English, so hopefully I uploaded the information accurately. Thank you! https://www.birdmapper.org/pages/explore-the-map