Below is some work that reflects on the regional characteristics, and specifically how borders in Northeast Asia have operated since the 1990s. It draws on research done as part of the NIHU Area Studies Project for Northeast Asia (NoA-SRC), based out of the Slavic-Eurasian Research Center, and my collaboration on the JSPS “Society and representations of 'territory' in Northeast Asia” grant, lead by Professor Iwashita Akihiro.
The NIHU Area Studies project concluded with an edited collection on Geo-politics in Northeast Asia, which is entirely Open Access.
Akihiro Iwashita, Yong-Chool Ha and Edward Boyle, Geo-Politics in Northeast Asia (Abingdon: Routledge, 2022) DOI: 10.4324/9781003288039
A few other pieces are noted below:
Edward Boyle and Akihiro Iwashita, Bordering and Scaling Northeast Asia, Asian Geographer 38.2 (2021), 119–138 DOI: 10.1080/10225706.2021.1894189
Illuminating Edges: Borders as Institutions, Processes, Space, in Green, Cathcart & Denney (eds.), Decoding the Sino-North Korean Borderlands (Amsterdam University Press, 2021), 27–44 DOI: 10.5117/9789462987562_ch01
Edward Boyle and Akihiro Iwashita, State Borders in Asia, in Sergei Sevastianov, Jussi Laine & Anton Kireev (eds.), Introduction to Border Studies (Vladivostok: Dalnauka, 2015), pp. 226–244 ISBN: 978-5-8044-1579-3