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Kai Shimoyama (下山 甲斐; shimoyama kai; d.1579?) is an Iga Ninja of Nabari. He appears in the Seishin (Pure Heart) series.


Draft of Kai (July 2021)

A ji-samurai, he was a member of a powerful family that guided the Oda forces, and was blamed for betraying the Iga to Nobunaga Oda. Therefore, he incur the Iga's resent. Before the revolt, Kai served as a guide for Nobuo Oda because he worked for the Kitabitake family. He likely served Kitabatake Tomonori (北畠 具教) until his territory was invaded by the Oda in 1569. In 1576, the Kitabatake were taken over as the main family was destroyed.

Kai is most likely from an honorary title, such as "Kai no Kami (甲斐守). He might've been a descendent of an Ashikaga vassal named Shimoyama Hachiro Shigesada (下山八郎重定), who lived in Nagaki; a castle was built in Hanachi (比奈知)


Is complying to Oda the reason why he turned a sword against his own countrymen? Or was there another reason?

There's a source staring that in 1579, before the Revolt, Kai no Kami visited Oda Nobuo and suggested that he finished the construction of Maruyama Castle, build by Nobuo's adopted father Kitabatake Tomonori. Its say that its due to protest of the "excess men of Iga" and their high military reputation. Why was there such dissatisfaction?


  • Birth: 1530
  • Death: 1582 (?)

Compared to real life counterpart, Kai has a less obscure role in the Seishin story as a member and rival of the Momochi Faction. His family's fortress is in Nabari Region. He served Kitabatake of Ise, which was once apart of Ise when the Imperials were strong, and eventually the Oda family that took over. His family served the southern court and said to have a strong personal ambition similar to Ashikaga_Takauji, which makes others wary of him.

He helps the Oda Forces to maintain the Tokugawa and Oda Alliance, and for increased stipend. During the Tenshō Iga no Ran, he comprised Iga to the Oda Forces, particularly to destroy Momochi. After the Second Revolt, he was given a high position within Wakisaka Yasuharu's arm, remaining consistent in turning his blade against his countrymen.

Much like Nobunaga Oda, he is strict and pushes order with force; "might-makes-right" type, but he also supports free will. However, he gives a more cool-headed atmosphere and has manners. Slightly stubborn. Adept in the bow, perhaps influenced by the Ban Family, and interested in sword and gun technique by the Oda family. Carried his own bajō-zutsu (馬上筒).

Draft Excerpt

Out of the Iga Trio, only Hayato was brave enough to approach Kai no Kami.

He seems taciturn. This man Shimoyama. Since the alliance, the man worked with Oda to fortify the alliance with Tokugawa (1562), who were once formidable rivals. Because of that, many of the Iga serving Hattori were uneasy around him. Hayate looked at him and he felt stalked by a viper hidden within the shrub. Not only that, there is story that Kai terrorize those of Suruga-Imagawa (and the Ohara vassals of Mikawa) for taking hostages, before the alliance was made. He was merciless, unmovable like a rock, and killed a child first. In 1568, he would take apart in scaring and dwindling the numbers of Anti-Oda movement (信長包囲網).

Hayate asked a strange question; he was asking for a friend. The answer? "A sword is for the hands of those who heed a leader. The same as a rifle. They both do the same thing -- kill."

Ninja Parameters

  • Ninjutsu - 4
  • Knowledge - 4
  • Battle Ability - 4
  • Heart – 5
  • Poetry – 2
  • Misc – ?

War Record/Events

Story Appearance