Owarimonogatari Episode 12: Shinobu Mail, Part 6
Episode 12 of 12 of Owarimonogatari, aired December 20, 2015, 25 minutes. Available with English subtitles and dub where released.
Episode summary
As Koyomi prepares for his duel, he learns of the crisis that Hanekawa is facing and must decide what battle he should fight.