She was also recognized as a Myustress, however she didn't claim that title until her disappearance in April 3, 2011 (Day1230), when she was presumed dead.
Born day 730 in eYakumo-cho, Hokkaido in Japan in Yagami family as a third child, Mion since the very beginning was educated to become a diplomat and also take duties of treasurer of Yagami Clan. After seeing the success of Akki's corporation, family send her to Tokyo to join SOS brigade, and train as a manager. However young Mion bored of no progress in her life left Japan and got into USA
However she still remained in USA, leaving all the company management to Aymay. On day 792 she got call out of nowhere from Brigade Chief Haruhi Suzumiya, (the content of this first talk was never released), which made her return to Japan the same day.
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As a member of Desu Workers' Party
She won a seat in a congress, starting from Shikoku region (originally DWP members were to run in Tohoku). Her trusting, naive behavior and childish appearance didn't make her any core member of DWP, but put her close to most of the active members. She also handed New Development Organization to Nata-kun and created party-managed Desu Eientei company for the gold found in Yagami Clan treasury.
In the same time she persuaded Kuroiunmei the secretary of immigration to let Aymay become accepted as citizen of Japan. After this Mion started to help citizenship applicants, by informing about immigration procedures.
She won second time in Diet elections in April. In period between April and May, she was a Revolutionary Guard soldier. In may 2010 , she has become a member of Puccho's Nihongo Kyokai. After PTO of Desu Workers' Party, and consequently it's merger with eSoS, Yagami M, then known as 'Mii' started to change her Omnomnom News form.
As a member of Sekai Shakai Sensen
In May 2010, she inherited a giant fortune of 70Gold, however she didn't used any of it. Instead she started to publish her Work of Cabinet series, which was meant to be first series of educating articles about Japan As another job she started to perform checks for Immigration Secretary Erumaron. While doing this she became friends with French ambassador Stephane Villedieu . Lesser activity in Sekai Shakai Sensen also known as World Social Front, increasing waves of trolling and general boredom and finally demerging of SSS made Mii want to disappear. Just before disappearance she joined Black Knights.
The dissapearance and reappearance of Yagami Mii
On Friday August 13 2010 she left a note and farewell letter as well as 30Golds that were given to Brigade Chief Haruhi Suzumiya according to Yagami's letter.
In this letter many individuals weren't mentioned, which led to controversies after her reappearance which happened in early December the same year.
After her reappearance in Japan, Mii was staying without party affiliation, dreaming of reconstructing Desu Workers' Party together with SpeedycatCRO, however she never realised any of the goals in the "Tripple Cat program" mainly due to changes that occurred during that time. Later she became manager of empress candidate Aisha Clan-Clan, and during the Empress Day Festival in December she joined United Lolies of Japan. It was probably directed by fascination of Great ULJ member- Tanaka Fujimori
New home in ULJ
While in ULJ Mii started a number of activities, as a Historian, ambassador, Diet member. She even planned to start in presidental elections. She also had very successful private eLife, and were planning to marry soon before her death.
Probably on 7th March,or some days before it, Mii discovered Myu in herself, as one of the first she realised it's existence. It led to creation of theory of the Myu - Myuism. At 8th March she was recognized as one of Myustresses of the Myu. Her spirit (or Data Ghost ) can be seen by some followers of the Myu - Myuists.
Death of Mii
Her story gained much popularity in Republic of China (Taiwan) in April 2012. Many copies of her biography written by an Taiwanese author Soultama were sold. Soultama also published a story in which he present alternative history where Mii survived and is starting in presidental elections. In this history he implies possible eTaiwanese origin of Yagami Mion by calling her "偽娘日", which can be translated as "acting as Japanese lady" or just "fake Japanese maiden".Yagami Clan denied to comment on that.
The rumours of her death, has been resolved, after she was spotted just fine in one of the meetings of Democratic Party of Japan, currently she's honorary member of Cherry Blossom Party, trying to advise it's leaders. Soon after in early June 2012, she started a campaign for position of Prime minister of eJapan.
Aoba Castle Kidnapping of Yagami Mii
After losing the elections, she went on a vacation break to visit Aoba castle. During night 6/7 June, an incident known as Aoba kidnapping case （誘拐事件青葉白 、 jp.Aoba Shiro Yuukai Jiken) has occured. On that day Mii has also started to use Yagami Mii as her official name.