Summary:

Mireille is a young girl, a lone-wolf type who happens to be one of the most talented assassins in the underworld. One day she receives an e-mail with the name of her next target: Kirika Yumura. The e-mail has an attachment phrase, "Join me on a pilgrimage to the past." and a melody that was playing from a music box when Mireille's parents were killed. Mireille, whose parents were killed by a mysterious assassin, and Kirika, a girl who has no memory of her past, eventually team up together as assassins.

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