"Ghost Rule" is an original song by DECO*27. It is one of his first songs after a brief hiatus in making music (at least in the VOCALOID field).
One interpretation of the song is that singer (Miku) is a compulsive liar, whose life has been ruined by her constant contradictions and lies. It addresses her remorse for her own actions, though believing she cannot go back anymore.
This song became an instant hit on Nico Nico, entering the Hall of Fame within the week of its publication. It later entered the Hall of Legend and exceeded over 10 million YouTube views. It also received lots of Vocaloid, Utau, and Utaite covers.

vocaloid.fandom.com

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SUDDENLY, I didn't use the original, so everything above was kinda useless to write

It's CUSTOM OST format!! Go ahead and download it first.
Used songs:

• For stealth: (except it's instrumental version in-game)

• For other parts:

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Actually, I planed to keep this to myself, because right now assault and control parts seems too short, but maybe I'm wrong.
As for now - Say whoa~