Artemis of the Transparent Sea - Part 2 - S1.E52

After being brought aboard the 999, Artemis reveals her history, how she departed her mother to acquire a humanoid machine body. Having to work to pay it off in a factory had its toll however, and she stole a ship and fleed. Artemis dies soon after and is brought to the heart of her mother, where she is absorbed into it. With Galaxy Railways headquarters planning to destroy the mother, Tetsuro cries out for them to not do it.