There is an organization, Death Brand, plotting to conquer the world.
Its member, Tachikawa Masashi, was spending his everyday life doing his work as a non-combatant grunt. One day, he was called by Executive Ragulia, and while they were talking, he suddenly lost consciousness. Then he awakened... both his hands had become tentacles!

"Hands!! My haaands!!"
"You have been remodeled with magic and so have become a monster!"
"M-monster?! Why me?!!"
"Truth is, because of the lack of a budget".
"...Seriously?"

Masashi, who was nonchalantly turned into a monster because of the reason he could not accept, requested to be turned back into a human. However, since it was decided by an organization, she could not arbitrarily turn him back, so his request was immediately rejected.

She told him that if he wanted to become human again, he needed to meet a certain requirement. And that is... to defeat two magical girls who disturb an organization, Mana Blue (Wien) and Mana Red (Fenice).

"Incidentally... should you refuse after all, you will be fired for opposing the organization. Will you look for another job in these circumstances?"
"It's too much! Are you not outright threaten me?! It's extreme!!"
"Hey, prepare yourself, would you? Knock them down properly and you will be able to return to normal."

And so Masashi, who was a non-combatant, has been assigned to fight magical girls as monster...

[Translated from DLsite]