Kai was the daughter of Ujinaga Narita, a retainer of the Hojo clan during the Warring States Era
. Legend has it that she supposedly aided her father in defending Oshi Castle from the forces of Hideyoshi Toyotomi
during Toyotomi's siege of Odawara in 1590. She donned armor and led a force of two hundred soldiers. However, when the forces at Odawara Castle surrendered, Kai's father followed suit and surrendered Oshi Castle to the Toyotomi.
Later, Kai and her father were put in the care of Ujisato Gamo. During her stay, a rebellion broke out, and following the death of her mother-in-law, Kai slew the rebel leaders. For the act, Hideyoshi Toyotomi rewarded her father with land and wealth.
Kai's ultimate fate in history is unknown. It is speculated that following the western army's defeat at the hands of Ieyasu Tokugawa's
eastern army in the siege of Osaka, she fled with both the concubine and the daughter of Hideyori Toyotomi and became a nun.
In Samurai Warriors
Kai was first made a playable character in Samurai Warriors 3
. The game depicts her as a warrior-princess character that is watched over by Ujiyasu Hojo
. A fiery young woman, she is treated like a tomboy by Ujiyasu. Her weapon in the game is a whip-sword
In Kai's story mode, she becomes acquainted with Kunoichi
and Yukimura Sanada
during a battle in which the Takeda aid the Hojo in fending off Kenshin Uesugi
. During the battle, she becomes smitten by Yukimura's good looks, instigating a rivalry between her and Kunoichi.
Later in her story, the game covers the battle of Oshi Castle. Kai, having matured since her first battle, successfully leads the Hojo into destroying a dam, washing away a large portion of the Toyotomi forces in the process. She then fends off Kunoichi and Yukimura before defeating Mitsunari Ishida
to end the battle, but afterwards she becomes distraught to learn that Ujiyasu has passed away.
Following Ujiyasu's last wishes, Kai and her allies join with the Toyotomi. When a rebellion breaks out, she defends both Ujisato Gamo and her father Ujinaga Narita. In the midst of battle, Yukimura and Kunoichi come to her aid, helping her protect her father and stop the rebel Magoichi Saiga
. Once the rebels are routed, Kai then takes down the rebellion's leader, whom the game depicts as Masamune Date
Kai's story ends with the siege of Osaka. After seeing how in love Kunoichi is with Yukimura, she becomes determined to protect both of them along with their lord Hideyori Toyotomi. After successfully leading the defense of Osaka Castle, Kai confronts Ieyasu Tokugawa and defeats him, securing victory for the western forces.
In Kai's ending, she and Kunoichi are in a castle with some other ladies. Kai suggests that she would look good in a pink kimono, but Kunoichi fervently believes otherwise and suggests something far less feminine. The two bicker for a bit before all of their attention is called by the handsome Muneshige Tachibana
, who they all fawn over until Muneshige's wife Ginchiyo
appears and asks what they're all looking at. As the other girls go back to discussing kimonos, Kai wonders if her former lord Ujiyasu is proud of the lady she's become.