The founder of the castle is considered to be Satake Yoshinobu (1570–1633). Yoshinobu was one of the six great generals of Toyotomi Hideyoshi. During the Odawara Campaign of 1590, he took part in the siege of Oshi Castle under the command of Ishida Mitsunari, with whom Yoshinobu developed a good relationship.
Kawanoe Castle is located on the small Wasi-yama hill near the port area of the Kawanoe district in the city of Shikokuchuo, occupying a central position along the northern coast of Shikoku Island. Kawanoe was also known as Butsuden Castle. The term “butsuden” in Japan refers to temple halls, and for this reason it is believed that a Buddhist temple once stood on the site before the castle was built. Due to its location at the junction of four provinces on Shikoku Island, Kawanoe held significant strategic importance and was repeatedly targeted by rival forces seeking military control over the region.
The founder of the castle is considered to be the Onodera clan. The Onodera were originally a minor clan from Shimotsuke Province and served Minamoto no Yoritomo (1147–1199), the founder of the first shogunate. The Onodera distinguished themselves in battle against the Fujiwara clan of the Ōshū branch and were rewarded with lands around Yokote. Around the 14th century, the Onodera moved to Yokote as their permanent residence. Their original stronghold was Numadate Castle, but after a series of clashes with the powerful Nambu clan, they relocated their base to the site of present-day Yokote Castle. It was likely during this time that the first fortifications appeared at the castle.
Wakayama Castle was built in 1585, when Toyotomi Hideyoshi ordered his uterine brother, Hashiba (Toyotomi) Hidenaga, to construct a castle on the site of the recently captured Ota Castle. The purpose of this construction was to secure control over the likewise newly conquered Province of Kii. Following an already established tradition, Hidenaga entrusted the project to his castle-building expert, Todo Takatora. Takatora carefully inspected the future castle site, personally drew up several designs, created a model of the planned castle, and took part in the work of laying out the grounds (nawabari). For the construction he brought in more than 10,000 workers and completed the large-scale project within a single year, which was considered extremely fast by the standards of the time.
Toyama Castle is located almost in the very center of the former province of Etchū and is surrounded by a wide plain with a large number of rivers. The very first castle on the banks of the Jinzu River was built in 1543 by Jimbo Nagamoto. The Jimbo clan were vassals of the Hatakeyama clan and governed the western part of Etchū Province. The eastern part of the province belonged to their rivals, the Shiina clan, who were also Hatakeyama vassals. Beginning in the 15th century, the influence of the ancient Hatakeyama clan gradually weakened, and as a result, the Jimbo and the Shiina fought constant wars for control of the province. Meanwhile, the forces of the Ikkō-ikki movement periodically intervened, helping first one side and then the other.
During the Sengoku period, the lands where Takada Castle would later be built were part of Echigo Province and were controlled by the Uesugi clan.
