Unabara Mitsuki (海原 光貴, Unabara Mitsuki?) is a character introduced in Toaru Majutsu no Index. The grandson of the director of Tokiwadai Middle School, he is most notable for being the person that Etzali has borrowed his appearance from.
He has a neatly combed dark-brown hair, and is dressed in a very orderly fashion. Unabara Mitsuki is described by Touma as someone who looks they were born from a painting;  Touma also mentions that he looks cool and elegant.
Judging from Mikoto's inability to distinguish between the two, it's implied that Unabara's personality is the one that Etzali fabricated while in disguise; that would be the character of a kind, straight and considerate young man that is quite modest about his great looks. While Unabara's grades are the best of his class, the fact that he got his rank through cheating might be his only evident personality fault.
It should be noted that once he managed to escape Etzali, he was more concerned about Mikoto's safety than with his own, desperately searching for her as to warn her about the upcoming danger.
In volume 5.5 of the manga Unabara gets a detailed profile, in which his main traits are : style, the power of the first impression, being noble, "gleam power", being a prince and (surprisingly) his unluckiness, though he is not unlucky to the level of Kamijou Touma (the book itself references this in ESP card terms, in which Unabara is unlucky at "level 4", while Touma's can be graded "level 6" with life threatening situations). It should be noticed that the author of the light novel, Kamachi Kazuma, was involved in the creation of volume 5.5.
He is the grandson of the director of the Tokiwadai Middle School; this fact allowed Etzali to get close to Misaka Mikoto quite easily. Before being abducted by Etzali, his relationship with Mikoto is described as acquaintances who will not interefere with each other's plans.
According to Shirai Kuroko's investigations, he actually got his grades through cheating. His method is to put a thin layer of his ability on the computer screen for the exam, feel the minute heat and radiation, and reverse-engineer the correct answer. This is one of the reasons that Kamijou Touma figured out Etzali is borrowing Unabara's identity, since the real Unabara is supposedly not that smart, while Etzali helped Touma do his summer homework.
A week before the events of August 31, Etzali abducted Mitsuki and later took his form. Mitsuki managed to save himself using his abilities, rendering Etzali's continued attacks on his body useless.
Unabara Mitsuki later managed to escape, knowing of Etzali's plans.
Toaru Majutsu no Index
Three Stories ArcMitsuki's only true appearance is after Etzali meets up with Touma for the second time while Mikoto is busy buying Touma lunch. Here, Mitsuki rushes through the crowded store where Mikoto was to tell her to run away.
He is later seen being taken away in an ambulance, right before Mikoto tries to find Touma who at this point is battling Etzali.
His ability is Level 4 Telekinesis (
He not only can use his ability to cover objects at a far distance, but he can also use his powers in his own body.
According to the novel, when Etzali attacked Mitsuki and peeled off some of his skin, severely injuring him, Mitsuki managed to save his life with his own power, which he used to petrify every cell of his body; this left him in a state that Etzali described as similar to "cryogenic stasis". In this state Unabara could not perform any actions, but also could not suffer any harm regardless of what attack Etzali launched at him. 
- Etzali disclosed that Mitsuki doesn't have any siblings. 
- His only actual spoken line in the anime adaptation is "Please escape!", said to Mikoto while Etzali was attacking Touma.
- Toaru Majutsu no Index Manga Chapter 023
- Toaru Majutsu no Index Light Novel Volume 05 Chapter 2 Part 7
- Toaru Majutsu no Index Light Novel Volume 05 Chapter 2 Part 13
- Toaru Majutsu no Index Light Novel Volume 05 Chapter 2 Part 1
- Toaru Majutsu no Index Light Novel Volume 05 Chapter 2 Part 11
- Toaru Majutsu no Index Episode 18
- Toaru Majutsu no Index Light Novel Volume 05 Chapter 2 Part 16
- Toaru Majutsu no Index Light Novel Volume 05 Chapter 2 Part 14