Gin no Kerberos

In the the near future, the Japanese government has succeeded in discovering and monopolizing a new form of energy known as Ψ ("Psi"). To protect this precious new energy form rival forces, the Japanese government created a three-man elite force known as "Cerberus." This team consists of: the "Princess" Sakuya, Gotou, and Leon. Gotou and Leon support Sakuya, who experienced a traumatizing past that still haunts her daily. Yet, she is the deadliest fighter out of the three. These three fight side-by-side in this epic science fiction world!

(Source: MangaHelpers)