Brother Mary is a crow member in Season 2 of Crow Cillers, first appearing in Episode 8. Her main focus is helping Brother Marcus explore the "Ynce Iche" and the effects it has on both reality and people. She grows frustrated with time as the "Ynce Iche" tunnels refuse to open and high ranking Crow officials urge her to stop searching for them.
When finally leaving Brother Marcus as she no longer wants to continue the search, she is shot and almost killed by him. This event leads to her joining the resistance towards the Crows as a double agent in Season 3.