TMdict

→To learn more about this problem child, go check out Fate/strange Fake.

One half of the El-Melloi Classroom’s legendary duo.
The blessed unwanted child. Or, more frankly, the idiot genius. Originally a character from Fate/strange Fake. For most of his lines, the author received assistance from his fellow writer, Narita Ryōgo. Though, Case Files and Fake have a number of key premises that are extremely different.
His elemental affinity is Void.
Normally, a magus is bound by what magecraft they specialize in. But in Flat’s case, he recklessly creates a new magical formula every time, and hardly ever relies on a preexisting magical Foundation. For this reason, he has the apparently glaring weakness of “being completely unable to use the same magecraft twice,” but he doesn’t care so much about that. Maybe that’s what it means to be a genius.
In most cases, he uses one of the following incantations.
Casting proactively: “Game Select” (“Interference, Start”) + “Game Over” (“Observation Complete”)
Casting reactively: “Play Ball” (“Intervention, Start”) + “Game Set” (“Situation Resolved”)
That being said, while the ruby text of “Game Select” may remain constant with each cast, the kanji are decided at the time of casting.¹ This decision is based both on Flat’s whims at the time and any changes he wants to make to the spell’s formula through the meaning of the incantation.
Though he may seem like an omnipotent cheat character, his hand-to-hand fighting ability is surprisingly zero. Or rather, negative. He fails out of every single self defense class. That is why even after Svin graduated, Flat was still unable to graduate from the El-Melloi Classroom. The scene of Svin coming back to the classroom and chastising Flat for still causing trouble for their professor has become a regular occurrence.
“I’ll ask just in case. Why did you do a drop kick for self defense?”
“Because it’s cool, Professor!!”
“Alright, die then. There’s no way a drop kick would ever be considered in a realistic self defense scenario, you absolute idiot!”
“But Professor, I believe he only failed due to his inexperience.”
“…please, Miss, don’t encourage him.”

Translator’s Notes

1. ^ In the Japanese text, Flat’s Incantations (like most Type-Moon incantations) are written as Kanji with an indicator above them as to how they should be read. This pronunciation guide actually spells out the English phrases (“Game Select,” “Play Ball,” etc). The Kanji below them show the intended meaning of the phrase, and is in Japanese (“Interference, Start,” “Intervention, Start”). The comment here refers to the fact that while the pronunciation guide of “Game Select” remains constant, the kanji representing the actual meaning that should be taken from the phrase are different for each casting.