Kanojo ga Flag wo Oraretara: Christmas? Sonna Mono ga Boku ni Tsuuyou Suru to Omou no ka?

Kanojo ga Flag wo Oraretara: Christmas? Sonna Mono ga Boku ni Tsuuyou Suru to Omou no ka? is a side story and bonus chapter to the original series, released with the 11th volume of the Kanojo ga Flag wo Oraretara light novel. It takes place concurrently with the main storyline, allowing readers to experience the events of Christmas through a different perspective with the girls who are part of Kokuhaku Flag, along with its protagonist.