Mysterious Heroine XX



  • Class: Foreigner
  • True Name: Mysterious Heroine XX
  • Gender: Female
  • Source: From Cosmo Guardian trilogy
  • Origin: Servant Universe
  • Alignment: Lawful Good
  • Height: 154 cm
  • Weight: 48 kg (changes when boarding)


  • Scenario writer: Nasu Kinoko
  • Character designer: BUNBUN
  • CV: Kawasumi Ayako
  • Main appearances: Fate/Grand Order


Magical PowerE
Noble PhantasmEX

Class Skills

Riding: [A]

Not only can she do Cosmo-Surfing by riding the Holy Spear Armor Arvalon[1] that has turned into flight form, but she can also steer the spaceship Stallion II.

Independent Action: [A]

It’s unthinkable that she was a former Saber class, but she has inherited the skill she had in the class from before becoming a Foreigner without change.
「That’s because, in severe missions, cool-headed self-assessment is required at times」, she herself is convinced with a triumphant look.

Existence Outside the Domain: [D]

Protection from the Farthest Ends, the extreme point at the exact opposite position of the Outer Universe.
As a result she became a Foreigner, but a Foreigner’s weakness is Foreigner so there’s no helping it. 「You throw a monster against a monster」

Cosmo Reactor: [B]

The protection of the great Universe (plot armor[2]) that draws towards herself victory’s principle of causality, but it has been ranked-down for being in the position of serving an organization.

Personal Skills

Boarding: [EX] [3]

The protection of the Holy Spear Armor Arvalon. The armor always exists around XX’s surroundings as Spiritrons.
To the quick work that materializes · arms this in minus 1 second (even if she receives a surprise attack, she goes back in time to one second before that and equips it), she has given the name of 『Boarding』. Almost automatic.
A fearsome skill that XX, who despite being a cosmic detective tends to oversleep in the mornings and is a recidivist of being late, has learned. Just a change of clothes skill.
Actually it’s not really necessary to materialize it, it displays its function as an armor even in Spiritron shape.
The BGM changes when using it… It has a sad anecdote in which she made that specification but it was rejected because that luxury wasn’t allowed for XX alone.
「You’re a swordsman Don’t pull an Assassin Put down That unruly hair on your head」

Instinct of the Detective: [E]

Revelation to determine the culprit. At a level that it’s better not to use it in case resolutions.
It generates a load of critical stars, but at the same time XX herself deals with a star concentration minus.
In some cases the demerit becomes a merit, it’s actually an excellent skill.
… She guesses the truth of the case with an 「I’ve got some insight!」, but it’s rank E so it becomes an incoherent conclusion. But that incoherent conclusion gives a revelation to the surrounding humans, and reveals the culprit after circling around. Generating a load of stars but not giving them to herself is because of this image.[4]

Justice of the Farthest Ends: [A]

Power from the 『boundary』 that is the forefront and farthest end of the Universe.
It’s the power to bite a hole in 『void』, and the truth that expands the Universe itself.
Adds invincibility penetration to herself, gains NP, and acquires 『special attack against Threats to Humanity』, truly a skill for the sake of a protagonist. Evil God Special Attack Artoria.

Noble Phantasm(s)

Mumei Seiunken - Unnamed Nebula Blade

  • Rank: EX
  • Type: Anti-Army Noble Phantasm
  • Range: 9~99

Mumei Seiunken. Secret-Myniad.
A galactic nebula cutter by using Rhongomyniad LR, which is said to be the heavenly scales of the Universe.
The beam of light produced by swinging the spear is a spiral like a nebula, and mows down all the surroundings. It doesn’t distinguish allies from enemies.
(Unused in 『FateGO』)

Æther Universe Howbeit the Order - Azure Gleaming Galaxy, namely Cosmos

  • Rank: EX
  • Type: Anti-Unit Noble Phantasm
  • Range: 9~99

Æther Universe Howbeit the Order.
She calls it things like 『Twinmyniad Disaster』 or 『Double X Dynamic』 depending on her mood on the spot, but the ruby (True Name) is 『Æther Universe Howbeit the Order』.
A True Name that mirrors the rules of the Universe that Rhongomyniad protects.
A dynamic Saber slash after releasing the safe mode of Rhongomyniad LR and increasing the output.
The opponent explodes with the planet.
A final means of judgment that doesn’t adhere to things like the right to remain silent or the right to call a lawyer.
A convenient Noble Phantasm that is not only a special attack against Foreigners, but a special attack against Sabers too.



First person pronoun: わたし (watashi)
Second person pronoun: キミ (kimi) / 〇〇くん (name-kun) / 〇〇さん (name-san)
Third person pronoun: 彼 (kare) / 彼女 (kanojo) / 皆さん (mina-san)


『Mysterious Heroine X』is, in a few words, the protagonist of a comedy drama.
X, who subtracted the serious elements from Artoria-san, acts in the shortest · fastest · simplest way for everything.
Contrary to her cheerful and polite conduit, she’s a very sore loser (since she’s not aware of it, her sense to read the mood is horrible) and will challenge you to anything, and she has a troublesome character that won’t give up until winning.
But since she “works for the sake of the surroundings in the end” due to her good nature, it worked well.

The Servant Universe came to a standstill too, and the hero-villain ratio collapsed due to the reckless firing of extra classes. When the heavenly scales of the Universe leaned towards the villains, X renewed her feelings.
Being specific, the program entered a new series.
X, who was in trouble for being unemployed, found a job at the secret society: the Galactic Police with the introduction of a certain Archer, and caught by accident the oldest artifact of the Universe: Rhongomyniad, which was sleeping at its center. Her talent was acknowledged, and she was appointed as a Universe defender[5] (Galaxian).

X thought 「This is a good chance」, and changed her name · family register to XX.
Having turned into a different person she trampled down all her debts until now,
and established the Special investigation Division 0 to enforce Foreigners, invaders from the Outer Universe.
The birth of the Evil God Hunter: XX.
Her instinct as a Saber Hunter has faded, and her instinct as a Foreigner Hunter stands out. That said it’s not as if she gave up the Saber elimination movement, so her special attack against Sabers is unchanged.

Attitude Towards Master

A partner at Earth. A reliable wallet.
XX’s love skills are nearly zero so there’s a sensation of friendship, but she realizes before long that they’re an important person, she makes mistakes like 「This throbbing in my chest… Could the evil god of Sabers be in this planet?!」 and misses her chance.

Dialogue Examples

She’s basically the same as X, but since she’s self-conscious (highly aware) of being a detective she behaves more like an older sister than X. Since it’s a series a few years after X, there’s the sensation of an OL tired of her life.

「Code-name XX, reporting for work! Yes!」

「Crush… Sabafes!」

「I mean… My identity was already found out… I didn’t prattle as I wanted… Secret talk during missions is strictly prohibited, so I used that low IQ speech」

「What with horror, that’s creepy! It’s decided that the best genre is sci-fi! I’ll prove it!
O’ spear of the farthest ends, your light here! Now seal the evil god, and bring the righteous
Big Bang
in this sector!」

Character in FGO

Appears in 2018’s summer event 『Servant Summer Festival!』.
In the early scenario, she descends as a Foreigner of unknown identity in Waikiki Street, and destroys as much as possible.
She seemed to be 『a new Foreigner observed by Chaldea』due to her outer appearance, machine voice, and her battle style in which conversation couldn’t be established at all, which made her only be seen as a mecha, but her identity was a special detective from the Galactic Police that had been dispatched to hunt Foreigner BB (Swimsuit), who tried to separate the Hawaiian archipelago from ordinary space and put it 『outside the Universe』, where nobody could intervene.
She is Heroin X from after some years, and XX alone knows that.
X washes XX away with a 「For some reason or another there’s a sense of familiarity but she’s unrelated to me」, and doesn’t realize she’s her future form.

Standard Weapons

Rhongomyniad spear style, a deed that doesn’t fear even God.
It’s a twin lancer style in which, when using the spear of light, the spear of darkness in the opposite side generates a backfire, and the opposite when using the spear of darkness.

Mysterious Heroine X

A Saber hiding infinite possibilities! There are some subtle differences with the me that is in my memories, but that’s a Universe-like plot hole[6]. With the remake and different narrator (director), the episodes subtly change… As they please?!

Mysterious Heroine X-A

…The resurrection flag is subtly rising… May there not be Mysterious Heroines A to Z…

BB (Swimsuit)

The first on the list of illegal Servants. Certainly, no matter how dangerous the event in the end she’s an ally of humanity, but… Everyone from Earth, aren’t you a bit too big hearted?


Eh… What’s with that wooden horse. Are you really a Servant from Pan-Human History?

Space Ishtar

And thus, the goddess of revenge became a normal Divine Spirit-type Servant. Happily ever after. Ah, but the story of the goddess isn’t over, it has to continue just a bit more.

Comment from the Illustrator

XX has big changes with Ascension, and since there are almost no common parts between each Ascension design, I drew each Ascension separately. While thinking that all of the transformations are striking, so I hope everyone likes any of them… in the end, she become a somewhat awesome character. During the work her last Ascension is the one who covers the least, but seeing her popularity the smile is the best! (BUNBUN)

TL Notes

[1]: アーヴァロン, different from Avalon (アヴァロン).

[2]: 主人公補正. Literally “protagonist modifiers”, but that sounds awkward.

[3]: 乗着. There’s no literal translation, it’s something like “Ride-Wear”. The most accepted translation is Piloting, but well…

[4]: See? This is how you describe a skill.

[5]: 防人. It’s a specific term to refer to soldiers stationed in Kyūshū in the past, or in remote regions of China during Tang dynasty, but I’m just leaving it as “defender”.

[6]: 設定齟齬. Literally “inconsistency in the setting”.

Material Images

(Lib will add after publish)