Blue Seed/WMG

The areas occupied by Japan in World War II were infested by Aragami
The ideas of Susano-oh and Kaede, while not caring much for Japanese people, otherwise are laced with extreme nationalist ideas about Japan. Such people, when deciding to take over "Japan" for nature, wouldn't define Japan by modern maps; they'd consider "Japan" to be all territories once claimed by the Japanese. This would include at least Korea and Taiwan and perhaps any square inch of land ever occupied by Japanese troops back then.