Hayashi Yoshikatsu served as a bushō from the Sengoku to early Edo periods. In the Edo period, he was a retainer of the Tokushima domain.
His family originated from the village of Kamibayashi in Owari Province and his ancestor was Minamoto no Yoshinaka (a bushō from the latter part of the Heian period). His descendants moved to the village of Uesugi and adopted the surname of Hayashi. Yoshikatsu served Imakura Samanosuke and, later, Oda Nobunaga. After the unexpected death of Nobunaga in a coup d’état on 6/2 of Tenshō 10 (1582) known as the Honno Temple Incident, Yoshikatsu participated in the Conquest of Shikoku initiated by Toyotomi Hideyoshi.
In 1586, after Hachisuka Iemasa entered Awa Province, Yoshikatsu became a retainer of the Hachisuka family, serving as the chamberlain for Kawashima Castle – one of the Nine Castles of Awa (nine outlying castles in Awa renovated by the Hachisuka Iemasa). Yoshikatsu, along with served to Takechi Nobuaki, served as a magistrate at Tokushima Castle. Thereafter, he joined the Conquest of Kyūshū and a deployment to the Korean Peninsula for the Bunroku Campaign. In 1596, Yoshikatsu retired and adopted the Buddhist name of Dōkan. However, at the Winter Campaign of the Siege of Ōsaka, he participated at the age of eighty-one, and received one hundred gold pieces in recognition of his contributions.