Nickname: Crystal Princess
Guren wore red lipstick, had fair skin, dark eyes and light blue hair which she kept in a spiky ponytail with long strands of hair framing her face. Her outfit consisted of a green dress with a long left sleeve and a short right one, a red turtle-neck which had a white, fluffy collar and brown gloves. Under the dress, she wore a one piece red suit. For shoes, she wore calf-length brown sandal boots.
As a child, she wore a teal short kimono with a grey turtle neck and short sleeves with a jade-green rope belt around her waist, and red shorts, light purple wrist bands and navy blue sandals. Also, the strands of hair that framed her face were shorter.
Guren has shown to be very mysterious, apparently preferring to keep to herself despite having a strong loyalty to Orochimaru. During her introduction, she quickly showed herself to be a remorseless and sadistic person. When told by Kabuto that several prisoners would be fighting to the death, she became ecstatic to hear there would be a slaughter. Guren is also shown to be vain by the fact that when she used her Crystal Release: Jade Crystal Mirror, she looked at herself and said, "Lovely, as always." She has also shown to be very proud. When Naruto offered to carry her, she was embarrassed because she felt it was shameful.
She is devoted to Orochimaru to an almost obsessive state. This devotion was so powerful that she fell into despair when she learned she would not become Orochimaru's next vessel, isolating herself from the shame. It has also been shown she has a terrible relationship with Kabuto, as the two argued often, trading scathing remarks. Later, she meets Yūkimaru, and at first, she finds him peculiar and somewhat irritating. However, when Yūkimaru became ill, she cared for him, watching over him for an entire night, until she fell asleep from exhaustion. When she woke up, she found that she was alone - and went searching for Yūkimaru, who she found nearby outside under a camellia tree. She then develops a sort of friendship with him as she crystallizes a flower and tells him that the flower will never wither as long as she is alive.
Since coming in contact with Yūkimaru, Guren seems to be having conflicting emotions. While part of her still wants to be accepted by Orochimaru as his next vessel, another part of her seems unable to let go of the bond she has made with Yūkimaru to the point of protecting him even from Orochimaru's right-hand man, Kabuto. The emotions seemed to have become more confusing for her in her first one-on-one confrontation with Naruto, who stated bluntly how horrible and selfish a man Orochimaru really is.
After realizing the truth behind her past and how it connects her to Yūkimaru, Guren feels even more compelled to protect him, out of guilt and repentance for her past sins, as well as love - wishing to become an almost surrogate mother to the boy, to replace the mother she killed. She even goes so far as to turn her protection to Naruto, as they faced off against the small Three-Tails clones within the beast's stomach, telling him she would protect him to the death if he would watch after Yūkimaru. This is a great change from her previous interactions with Naruto, whereas she was stand-offish and combative, she becomes quite friendly with Naruto. Subsequently, Guren has also begun to have doubts over remaining loyal to Orochimaru, due to her grief over the horrible things she was made to do in his name, and the damage and pain he has caused Yūkimaru and herself.
As a child, Guren came from a small village where she was shunned by others because she had unique powers. Later, Orochimaru appeared and destroyed the entire village single-handedly. He was intrigued by Guren's powers and offered for her to come with him. Guren chose to follow him because she envied his power.
At some point, Orochimaru sent her to destroy another town in order to test her potential. However, after doing this she passed out, due to the over-usage of her powers. When she woke up, she found herself to have been healed by a woman, who she would later discover to be Yūkimaru's mother. Guren returned to Orochimaru but, in order to keep his approval, she was forced to kill the woman. Wanting Orochimaru to accept her, she sadly killed the one who had cared for her.
Guren quickly became one of Orochimaru's most powerful and loyal subordinates. Eventually, she was offered the chance to become one of Orochimaru's future vessels. When Sasuke Uchiha defected from Konohagakure and Kimimaro was no longer a suitable vessel for Orochimaru, Guren became the next best choice in Orochimaru's eyes. Unfortunately, by the time she arrived, Orochimaru couldn't wait any longer and instead chose Gen'yūmaru. Feeling no longer of use to Orochimaru, Guren went into isolation.
To aid him in final preparations for his plan, Orochimaru sends Kabuto to fetch Guren (much to Kabuto's disapproval). Guren attacks him when he approaches her domain, but he is able to avoid her attacks. When asked why she attacked him, Guren states that she just wanted to make sure Kabuto was worthy of being Orochimaru's right-hand man.
Upon returning to Orochimaru's hideout, she has hundreds of Orochimaru's prisoners fight to the death and forms a team with the survivors: Rinji, Gozu, Kigiri, Kihō and Nurari; sixteen other survivors tried to rebel, but Guren killed them all.
Guren, disapproving of Sasuke's status as Orochimaru's next vessel, is later offered a chance to replace Sasuke if she can prove herself. She and Yūkimaru are sent to a certain area. While there, Yūkimaru gets sick, forcing Guren to care for him. When he recovers, she is surprised to learn he too knows what it is like to have no-one at such a young age, and seems to have grown some feelings for him. She then crystallizes one of his flowers, knowing how much he likes them, so it won't wither as long as she is alive. Later, when finally meeting back up with Team Guren, she leaves Yūkimaru at the hideout while she goes out to handle Team Kurenai.
"Lovely, as always."
While her men fight Team Kurenai and Kakashi, Guren prepares for their arrival. Once done, she has her men fall back, drawing the Konoha ninja into a trap and allowing Guren to encase Hinata in crystal. She uses Hinata as a hostage to prevent her men from being followed. Before anything can be done, Team Yamato arrives and breaks through her traps and defenses, and subsequently frees Hinata. Annoyed at her enemies escaping, she decides to return to their hideout to plan their next move, but Kabuto arrives and reveals another plan.
Kabuto, Guren, and her men go out to the lake so that they can awaken the Three-Tails. When it appears, she tries to restrain it but proves no match for its strength, the whole time holding Yūkimaru in a protective hug. She uses the last of her chakra to save Yūkimaru and the others, and later awakens to find herself in the care of Yūkimaru. Yūkimaru, however, is sick again, speculating that it was because of Kabuto's overdose of pills. While taking care of Yūkimaru, she detects Naruto coming and intercepts him. After a short scuffle, Yūkimaru appears to stop the fight. It is here that Guren hears another view of Orochimaru from Naruto, making her question the path she has taken.
After escaping with Yūkimaru, she and her team begin preparing for the final confrontation with the Konoha ninja, Guren hoping to face Naruto again to settle things with him. After engaging them she is forced on the defensive and almost defeated, but Gozu sacrifices himself to allow her to escape. Guren flees but is pursued by Naruto, who makes it clear to Guren that he's determined to take Yūkimaru away from her no matter what. Guren assumes that Naruto's interest in Yūkimaru is solely because of his connection to the Three-Tails.
When Guren returns to Yūkimaru, she hears him playing a grass-whistle. The melody causes her to realize that she was the one who killed his mother. She begs Kabuto to not put Yūkimaru through any more pain, instead offering her own services to stop the Konoha-nin from sealing away the Three-Tails. Though she proves successful, the Three-Tails begins attacking her, and it is only through Yūkimaru's interference that she is saved. Seeing how desperate Yūkimaru was to protect her, Guren's guilt towards the boy becomes greater than ever, knowing that the boy was clinging to the person who had killed his mother. Deciding to atone for her crimes to Yūkimaru, Guren chose to do everything in her power to protect him. Guren, with Naruto's help, attacks the Three-Tails, but it eats them both.
Though Guren tries to resume her fight with Naruto within the beast's stomach, he instead tends to her wounds. The two quickly begin arguing about where Yūkimaru belongs. When Guren accuses Konoha of wanting to capture the Three-Tails for their own means, Naruto says that is not the case. Guren does not believe him until she learns that he is the jinchūriki of the Nine-Tailed Demon Fox, something that earned him much hate from his fellow Konoha ninja. Upon learning that Naruto refuses to use his demon's powers in fear of hurting his loved ones, she begins to see that Naruto is genuinely concerned for Yūkimaru's well-being.
Guren admits to Naruto her hand in causing Yūkimaru's loneliness. After revealing the truth, she decides that Naruto is right, that Yūkimaru's place should not be with Orochimaru nor her, but with Naruto. Her sincerity towards this statement is proven by her desire to make sure Naruto gets out alive. To her surprise, however, Naruto says she has changed and can make up for her mistakes. Together, they manage to escape from the Three-Tails, only to discover that Yūkimaru is again being used to control the Three-Tails.
Guren and Naruto arrive in time to save Yūkimaru from being forced to take a strange drug from Rinji, who turns out to be Kabuto in disguise. Kabuto reveals the truth to Yūkimaru, which Guren makes no attempt to stop. To her shock and joy, Yūkimaru decides to forgive her. The two then admit how much they mean to each other. Guren goes to leave with Yūkimaru under Naruto's orders, but Rinji's reanimated body pursues them. Guren battles him in an attempt to protect Yūkimaru. Guren tried to trap Rinji in her Crystal Release, but he used his bats' supersonic abilities to shatter the crystal, saving himself and subsequently stopping Guren from using her Crystal Release. Determined to protect Yūkimaru, she went behind Rinji and kept his hands apart to prevent him from using his techniques and controlling the bats. Though unable to perform any hand signs (with her hands busy holding back Rinji's arms), Guren still managed to use the Crystal Release and crystallize herself and Rinji. The two fell into the water below. Gozu later saves her. Gozu stated that his reason for saving her was because he looked up to her since the day she saved his life by giving him a ladle of water to drink when he was on the verge of death from dehydration. Yūkimaru later joined up with them, and the three of them left together.