Love, Chunibyo & Other Delusions: Glimmering...Explosive Festival (Slapstick Noel).

Episode 13, included in the final volume of the BD/DVD. Taking place directly after the events of Chuunibyou demo Koi ga Shitai! , Christmas is coming up and Rikka is told by Nibutani that this is an opportunity for her to get closer to Yuuta. Under Makoto's suggestion, they plan a Christmas party at Sanae's Mansion.