1x13 - Haibane Renmei

Rakka discovers that Reki's entire studio is painted like her cocoon dream. She gives Reki a box from the Communicator, containing her true name, which fills Reki with despair. She throws Rakka out of the room, confronts a manifestation of herself, and relives her dream. Rakka realizes the truth about Reki's struggle and goes back to save her.