The Akari arc in episodes 9 and 10. "Thank you, Daddy."
The events of Episode 11. Although it soon turns out she's still alive, everyone's reactions to Maya's "death" hit quite hard, especially Fumiaki's.
Chihiro is mortally wounded by Mikaze stabbing her (note the stabbing sound after Mikaze told her Fumiaki kissed her, her panther familiar crying for her as she gives a prayer for Fumiaki's success, and the red bloodstain on her back when Maya reveals how she still has her father's notebook protecting her). When Mikaze is defeated via a spell that destroys evil, Chihiro's body has disappeared.
"That is a spell to destroy all demons. Those born of the darkness must return to it. May good fortune be upon you..." Chihiro's demonic panther familiar disappears via the same spell that defeats Mikaze since it affects all dark magic, good or bad.
After you let it sink in, the final episode definitely counts. The sacrifices of Chihiro, her familiar, and especially Fumiaki were ultimately necessary to avoid the Bad Future, and Maya reunites with her father for dinner in the new timeline as members of the Uchida household.
