This is the "Military Man" decal for your Arsenal that uses calligraphy from calligrapher Souun Takeda.

The in-game design does not contain Mr. Souun's signature.
A copy of "DAEMON X MACHINA" will be required to use this content.
This content is purely cosmetic, and using this will not have any status changes.

More details on the official game page of Arsenal Decal "Military Man" ...