Shiori (Her real name is Luna) is one of Fate's Ministra magi who disguises herself as Asuna with her artifact Signum Bioregen ("Life-Stealing Mark") while the real Asuna is kidnapped by Fate.
Luna, as she was known then, met Fate when he experienced a malfunction and fell out of the sky. Luna's older sister brought Fate into their home to allow him to recover, though neither Luna nor her sister could read Fate. Fate discovered he had a taste for Luna's sister's coffee and when he left three days later, he was invited to return whenever he wanted for more. When he eventually does so, humans have attacked Luna's village, severely injuring her sister and leaving both on the ground far outside their home. As Fate speaks with Luna's sister, Secundum brutally murders her -- which he tries to justify because of the dangers of her telepathy -- to send her to CE, which is witnessed by Luna. Luna flees in fear and is about to be murdered by Secundum when Fate intervenes and beheads him instead. After that event, Luna joins Fate (possibly under the code name Shiori from then on) and is with Fate when he first met Homura and Shirabe/Brigitte.
Currently, Shiori has recieved far more focus than any of the other girls in Fate's harem. She spent most of her time convincing Ala Alba that she was indeed Asuna, so Fate could carry on his plans without suspicion from Negi. Suspicion was initially cast upon Shiori's identity when she was attacked by Kurt Godel, with an attack Asuna's magic cancel should have countered. Her injury results in Negi making a vow to protect Asuna -- a move that strengthens Asuna's (and consequently Shiori's) affection towards Negi, temporarily weakening her artifact.
Shiori continues to fool Ala Alba until Cosmo Entelecheia's attack at the Governor's Ball. At this point, Rakan's parting words to Negi advise him the Asuna traveling with him is likely an impostor. After the escape from the ball, Negi remember's Rakan's words and wants to confront Shiori face-to-face inside the Diorama Sphere Theodora provided. Chisame, who was also with Negi during the reveal, follows Negi into the sphere with Mana and Nodoka. When Nodoka's mind-reading fails to prove Shiori's identity, Mana suggests they shoot her with an anti-demon bullet to expose her true form. Amidst the chaos, Negi decides to reveal Shiori's true identity with a pactio. The kiss causes Shiori to completely fall in love with Negi, weakening her disguise and revealing her true identity.
Shiori, whose true name is revealed to be Luna, is then interrogated by the others. Since Fate told her she was free to do whatever she wanted when her mission was over, Luna decides to tell Negi that Cosmo Entelecheia has kidnapped Asuna and Anya, and is holding them hostage in the Gravekeeper's Palace. At this point Luna decides to aid Negi and the others in their assault on the Gravekeeper's Palace, despite suspicions from Mana. Chisame is quick to note Luna's crush on Negi; however, she still appears to have great respect for Fate and is fiercely defends his actions when they are under criticism. Her conflicting feelings for both Negi and Fate cause her great personal confusion, as well as criticism from Negi's party and her own.
Upon leaving the Diorama Sphere, she resumes her Asuna personality to not worry the other girls about Asuna's kidnapping. As a member of Cosmo Entelecheia, she is able to provide Negi's team with many useful details, like a secret opening in Fate's barrier around the palace. Up until the confrontation with Dynamis, Tsukuyomi, and the other Fate girls, Luna was traveling in Kaede's artifact, helping navigate the others throughout the palace. After Dynamis used the Grand Master Key to cause her and the other people in the cloak to come out of hiding, she, along with Negi, Chisame, and Nodoka, tried to go on ahead to retrieve the Great Grand Master Key. However, an attack by Dynamis caused Negi to become corrupted by the Magia Erebea again, causing him to severely damage Dynamis. However, before Negi can deal the final blow, Luna reverted back into her regular form and, trying to stop the corruption from the Magia Erebea, took the attack that was intended for Dynamis. Luckily, she was only grazed and Konoka was able to heal her, although the attack resulted in Negi going into an unconscious state.
After being attacked by Sextium, she was saved by a freshly-awoken Negi and is viewing the final battle between Negi and Fate.
- Artifact: Signum Biolegens: Shiori kisses the target and transforms into him/herself in both mind and appearance. The target's emotions will be transferred to the user. For example: If the user falls in love, the power will be broken, as shown when Negi kissed the fake Asuna to reveal her true identity. The auto-suggestion aspect of the artifact, which completely hypnotizes Shiori into assuming the target's identity, is shown to be powerful enough to fool Nodoka's artifact. Shiori's artifact is able to replicate the user's (Asuna's) artifact, but not its abilities. The same appears true for natural abilities, like Asuna's magic cancel. As of chapter 292, it appears Shiori can speak to the persona of the person she is imitating, and maintain they can switch personalities and speaking at will. However, this would usually be out of character and thus draw suspicion to her disguised self.
- Mind Reading: Shiori's people are supposed to be able to read the minds of people whom they touch (with a kiss based on how her sister attempted to read Fate's mind). Shiori has not yet demonstrated this ability. However, it is implied this is how Shiori is able to use her artifact so successfully, and why she kissed Asuna to take on her appearance.
- She's the only Fate Ministra Magis who has a Pactio card with Negi; her new Artifact is still mysterious, however it looks like she still have the same artifact as before (Signum Biolegens). It is the only pactio card thus far to have the rare "prisma" tonus.
- The roman numeral that is shown on the top left and bottom right corner on her card shows (XXXII) which may imply that she will become one of Negi Springfield's students.
- Shiori's artifact has belonged to Fate in the past. He is seen using the Signum Biolegens ten years ago against Ala Rubra.
- In one of the statements in the picture Shiori says "This Signum Bioregens that Fate-sama perfected over ten years" implies that Signum Biolegens might not be the same as it was. This is a reference to the flashback Chapter 231 when Fate uses the artifact to impersonate Senator McGill. When Nagi sees through his disguise, Fate comments that "more research will be necessary."