Gisen Yagyu (柳生 義仙 Yagyū Gisen) is one of the main antagonists of Hyakka Ryouran Samurai Girls
A very mysterious character, both in appaerance and behavior, but even though a powerful and decieving Master Samurai of high ranks. She is superior in swordsmanship and a master of manipulation.
Gisen is a young girl with silver-colored hair of a average height, as she appears to be in the same age as Jubei, and has a very attractive figure. At first she appears to Muneakira and his friends as a amnesiac with no recollection to her past except her name, as she falls naked from the sky into Muneakira's arms, much like Jubei. In the beginning she wears a simple white kimono with a length only to above her knees, and is friendly to all in her assocciation. But she also has a behavior to be shown as very perverse when around Muneakira (whom she refers to as "Master"), wanting to "tuck in" his body parts (implying to be sexual intercourse), the reason being is that she usually thinks that the relationship between a general and a samurai is similar to that of a master and slave.
However, it is later revealed that she is a Master Samurai, with the concentral mark on her right eye. When transformed she is dressed in a traditional white-colored seifuku (a Japanese school uniform that is modeled on European-style naval uniforms), wearing black stockings and red shoes. Under command of Shiro Amakusa, a powerful samurai who aspired to destroy Japan until he was killed by a group of rebels, she eventually intends to revive him so he can destroy Japan once more. Her transformation phrase is "Inka Ryōran", which means "Indecent Flower Blooming Profusely", and her attacks usually revolve around ice. Gisen's right eye (colored red) can control and manipulate people's minds, and she wields a blade that can turn into a scissor-like weapon.
In her first initial appearance to the Yagyu Dojo, Gisen is portrayed as a friendly and well-meaning young woman to everyone, except the fact that Sen and Yukimura is suspicious having her around. When she introduces herself to her new friends, they are all surprised to know that her last namn is Yagyu, just like Jubei and Muneakira. But as friendly to the other girls in the dojo, Gisen is shown to be very perverse when around Muneakira (whom she refers to as her "master"), wanting to "tuck in" his body parts (implying to be sexual intercourse), the reason being is that she both in secret and official usually thinks that the relationship between a general and a samurai is similar to that of a master and slave. Her true personality is also revealed throughout the story, displaying her as a highly sadistic person who will stop at nothing to ensure her general's revival; she even attempted to take Jubei's body into her own to further the process.
One evening, when eating dinner in the dojo, Muneakira and his friends suddenly notices a unknown light from the outside and goes out in the garden to investigate followed by Jubei, Sen and Yukimura. When he then looked above he saw a mysterious girl who fell from the sky, in exactly the same manner as Jubei once did. He raised his arms to the heavens and catched the visitor. He noticed that the girl was wearing an eyepatch but not understood why. The girl then opened her eyes and tried to kiss him, but then Jubei stopped them, telling Muneakira not to kiss her because she at first didn't like the behavior. No one understood why Jubei act like that so sudden, but the new girl just gave her a smirky smile and didn't say anything. When the girl later introduced herself to the group as Gisen Yagyu, princess Sen and Yukimura immediately become suspicious to her. Due to her initial "amnesia" Muneakira let her reside in the dojo until she had regain her memories, which Sen and Yukimura naturally was against because they don't actually knew her as well, and as Gisen begun to act extra friendly to Muneakira the distrustfulness against her grew.
The next morning, when Muneakira washed himself, Gisen walked in to him. Muneakira, unnoticed about her company tried to grap a towel to dry his face, he accidentally took a grap on Gisens left breast. When he finally regain his sight, he immediately drew himself away from her as he didn't mean to do that, but Gisen said in a flirty way to him that he could to anything he wanted to do with her. But as Muneakira was a kind och generous young man he refused to do that, despite Gisens personality, both gentle and sexual. The second after she get herself onto him, the door opened and Sen och Yukimura come in. Angered by Muneakira's present position, in thought that he begun to seduce Gisen, both of the girls activated their powers and punished him. When they walked away from the bathroom, repeately comment about Gisen and her suspicious behavior, none of the friends noticed that Gisen had sneaked upon them and snatched Muneakira away. Both Sen and Yukimura begun to search every corner of the dojo in anger for Muneakira, believing he had ditched them for Gisen. Unaware to them, Gisen had actually "kidnapped" Muneakira to have more fun with him in her own ways. Hidden away from the angry princess and Yukimura in the toilet room, Gisen begun to seduce the young Samurai even more, despite Muneakira's constant refusal against it. Eventually, however, Sen and Yukimura found both of them still believing that Muneakira was continuing to ditch them for the new girl. This time Muneakira was beaten up more by the angry girls then before, later in the dojo Sen and Yukimura began to question Gisen out. The conversation eventually became a really hard fight between Gisen and Sen to decide which one of them who had the rightful essence about the true relationship of a general and a Samurai, the battle eventually ended with Gisen who was going to finish the princess off with her own hands was interrupted Jubei. The conclusion come to that Gisen realized how wrong she had act towards everyone and was allowed, with some of the resident's refusal, to stay in the dojo and formed a special sisterly bond with Jubei. In the heat of battle, Muneakira come to wonder who both Gisen and Jubei really was.
A short time later when Muneakira, in his doughts about making a pact with the other girl's in the group, cleaned the entrance to the dojo, Gisen, in the way of her usual habits, sneaked upon him from behind and tried to surprise him. Gisen then drew Muneakira with her to the old shed in the garden to seduce him again, this time the process included adult magazines, Gisen undressing herself and trying to become Muneakira more near than ever. But when Muneakira finally decided about the pact between Yukimura's partner Matabei, princess Sen's handservant Hanzo and Kanetsugu Naoe the situation eventually changed. Gisen revealed her true evil colors against her new friend and brainwashed him with her red eye, making him her mindless servant. When the rest of the girls in the dojo later come to search for Muneakira, Gisen turned Muneakira against them as a fiend. It was at this time that Sen's older brother and current Shogun of the Great Japan, Yoshihiko Tokugawa, and his own Master Samurai, the young French girl Charles d'Artagnan (nicknamed "Nia") returned from Paris and stood up against Gisen. During the battle Gisen revealed that she actually was a Master Samurai and that her General in reality was Shiro Amakusa, a Samurai who tried to destroy the country long ago, and now planned to do so once again. The battle was at a beginning very vicious but in the end Gisen decided to flee the field to battle another time, the ending of the battle stated the fact that Yagyu Dojo was taken under control of the Tokugawa Government forces under command of Nia where both Yukimura, Matabei, Hanzo and Kanetsugu was temporarily arrested and hold under costudy while Jubei, Muneakira and Sen was send to Yoshihiko's headquarter. Yoshihiko, who was determined to protect both his country and its people, had begun countless experiments in order to create a new generation of Master Samurai. To do so he had in secret taken many girls of the famous Buou Academy, who actually was descendents of legendary Master Samurai from long ago, in custody, which was blackmailed by the Japanese media as a so called "spirited away" incident. All this in order to prevent Amakusa from being resurrected.
At that time Gisen had taken over the Buou Academy and begun to reaweake her beloved General, so that he would once more spread his message onto the people of Great Japan, unaware of what Yoshihiko had done to her sister and "master". Unfortunately, her powers wasn't enough to rise Amakusa from the dead, and decided to use Jubei's powers upon him as well for success. Muneakira and Jubei, who had been prisoned by Yoshihiko, was eventually able to brake themselves free by a little assistance from Sen and Yukimura. Once freed, Muneakira maked his usual contract with Jubei and once again awoke the Master Samurai inside her. When Jubei had been fully released she begun to battle against both Nia and Yoshihiko, in order to make a clear way into the Academy so they all could defeat Amakusa. The short battle between the Shogun and the Master Samurai unfortunately caused most of the laboratory to break, in which destruction Nia was so badly injured that she died trying to protect Yoshihiko. Later, when Muneakira and all of his Samurai was gathered, the last fateful battle against Amakusa and his spawn was begun. With the help of Sen and Yukimura and under Muneakira's command, Jubei was able to break trough the barrier that Gisen had built up over the Academy during the resurrection ceremony and eventually managed to fight her sister herself. During the battle Jubei's innocent self reawoke inside her and took a shared control over her body, with both her personalities in action Jubei was successfully able to finally defeat Gisen once and for all but at, as it seems, the cost of her own life. What is becoming of Gisen is not shown, and Amakusa remain dead but mysteriously disappeared from the face of the Earth.
In the second season Gisen returns to the dojo fully alive, alongside Jubei, this time as a main character. Despite still having her old personality remained, she is now portrayed as the friendly character that she was at the first time the gang met her. When she comes back she has in a mysterious way temporarly lost all of her powers as a Master Samurai and is now harmless and innocent, possibly as a price to pay due to the fight with Jubei. When she first reappaers at the dojo, during this time redone into a maid café in order to pay back high bills to the government, all of the group, except Jubei who still sees Gisen as her friend, is suspicious against her. Under the overseeing of Jubei she is eventually accepted into the group, which also make it possible for Jubei and Gisen to reconcile as sisters.