- "The Rare Hunter of Love and Courage, Mireille is here!"
- — Mireille —
Mireille's PC is a young, pink-haired girl dressed in loose fitting blue and white robes. She wears an oversized hat with attached ribbons that hang down to the ground. She is identical in appearance to Mistral, though her character is somewhat shorter in stature than her mother's. Her wave symbol is printed onto her clothing.
Like her mother, Mistral, Mireille is shown to be a bright, optimistic character. She is always eager to help and please anyone around and will stop at nothing to obtain rare items.
Mireille roleplays as a "Rare Hunter" or rare item collector. She spends most of her time within The World exploring dungeons and clearing events in attempts to gain more rare items to add to her collection. She maintains a small hideout in Mac Anu (a rare item itself) which she uses as a storage shed for all of her items. She is very well connected within The World, and has ties with many powerful people inside of the game. Ouka the Divine Fist, one of the most powerful players in the game is a close friend of hers.
Mireille's player is Mirei Kurokawa, the four year old daughter of Mayumi Kurokawa. She is very close to her mother, who gave her PC to her daughter as a gift. Despite becoming wrapped up in the legend of The World herself, she was unaware of her mother's status as a .hacker.
Mirei is a child prodigy, with an IQ of around 200. By age 5, she speaks English fluently, and NASA (not knowing her age) has tried to recruit her. Her tutor expects that she will take her university entrance exams within a few years.
Mireille follows the newbies Shugo and Rena after mistaking them for the legendary heroes Kite and BlackRose. She watches from a safe distance as they fight a Data Bug with Balmung, which Shugo defeats using his Twilight Bracelet. Intrigued she reveals herself to them and introduces herself as a Rare Item Hunter. She quickly forces her way into their party, and drags them throughout The World to various events so they can help her get rare items. She soon introduces them to her friend Ouka, who joins up with them as well.
Mireille played a side role during most of the anime, though her rare items proved useful numerous times, especially when it came to disguising Shugo so he could sneak past the Cobalt Knights. During the final fight against Morti, Mireille was one of the few members of Shugo's party who was restored by his Drain Arc, allowing her to participate in the battle.
Drawn to the rare models of Shugo and Rena and intrigued by the Twilight Bracelet wielded by Shugo, Mireille introduces herself to the pair. As a mid level character she offers to help them level up quickly in exchange for any rare items they get. Needing the help of a caster Rena accepts her proposal and Mireille becomes a member of their party. With her help Shugo and Rena find themselves being dragged to all sorts of limited time events in search of rare items. It is at one of these events that they are introduced to Mireille's friend Ouka who also joins up with them. When Shugo discovers Zefie it is Mireille who is able to identify her as a Vagrant AI. As Shugo's party helps Zefie in her search for Aura Mireille is forced to call on all of her contacts, including the enigmatic Wiseman who tells her about the events that occurred "four years ago". Combining her information with information gained by Rena and Hotaru Mireille deduces that they need to travel to Net Slum. Unfortunately Shugo's party is captured by Kamui and the Cobalt Knights soon afterwards. Threatened with character deletion Mireille is forced to abandon Shugo.
At her hideout Mireille starts crying like a little girl which is when her real self really is a four year old child, Mireille is encouraged by her mother to do what she thinks is right. Mireille realizes that she wants to help Shugo at any cost, and mobilizes Ouka and Hotaru to help them out. Following a plan engineered by her mother, Wiseman, and Helba she reconnects with the rest of the party, including an escaped Shugo at Hulle Granz Cathedral. There they are met by the .hacker Kazu who delivers Shugo a key allowing him access to Net Slum. Though Kamui and the Cobalt Knights attempt to stop them Ouka and Kazu hold them off, allowing Mireille and the remainder of the party to escape.
In Net Slum Mireille watches as Shugo fights against Balmung for information that would allow him to locate Aura. Using advice from Mireille and the rest of the party Shugo succeeds in passing Balmung's test. But after Balmung reveals that only three people can access Aura's domain Mireille has no choice but to remain behind in Net Slum. Exhausted she logs off and goes to sleep, allowing her mother to take over her character and chat with her old friend "Bal-tan".
Mireille has a brief appearance at the end of Rumor where she meets with Brigit, Rena's former character. When Shugo logs in Brigit switches back to Rena and along with Ouka they all go on an adventure together.
In Rare Hunter, a bonus story in the Legend of the Twilight Manga Mireille runs into an item hacker named Luke. Though initially pleased with the large number of rare items he possesses, she grows angry with him when he reveals he obtained them by hacking. She declares that a true Rare Hunter only collects items legitimately, and that hacking defeats the entire purpose of item collection. Wanting to prove her point, she drags Luke with her into a high-level dungeon. Although the two nearly die before reaching the Gott Statue, Mireille is successful in showing Luke how rewarding finding a rare item can feel. Impressed, Luke deletes his hacked items and swears to become a true Rare Hunter himself.
- In the .hack//Games, Mirei was mistranslated as being a boy.