Kōō
Kōō, also romanized as Kō-ō, was a Japanese era name of the Northern Court during the Era of Northern and Southern Courts after Kakei and before Meitoku. This period spanned the years from February 1389 to March 1390. The emperor in Kyoto was Emperor Go-Komatsu The Southern Court rival in Yoshino during this time-frame was Emperor Go-Kameyama.
Nanboku-chō overview
This illegitimate Northern Court was established in Kyoto by Ashikaga Takauji in 1336. Until the end of the Edo period, the militarily superior pretender-Emperors supported by the Ashikaga shogunate were incorporated in Imperial chronologies, even though the Imperial Regalia were never in their possession.During the Meiji period, an Imperial decree dated March 3, 1911 established that the legitimate reigning monarchs of this period were the direct descendants of Emperor Go-Daigo through Emperor Go-Murakami, whose Southern Court had been established in exile in Yoshino, near Nara.
Change of era
1389, also called Kōō gannen: The new era name was created to mark an event or series of events. The previous era ended and the new one commenced in Kakei 3.In this time frame, Genchū was the Southern Court equivalent ''nengō.''