The death of Orimura Ichika!Phantom Task has gained control of the English anti-IS orbital cannon "Excalibur" after a successful raid, but things go wrong when the controls stop responding and it begins to de-orbit. Meanwhile, Cecilia scores a theme park birthday date with Ichika on Christmas Eve, but that glimmer in the sky isn't a romantic flurry of snow—it's a barrage of lasers from Excalibur! Amidst the commotion, Chelsea appears in the third BT prototype, challenging Cecilia to a duel. And the remaining cadets scramble into action to fulfill their special orders: the destruction of Excalibur before it wreaks any more havoc. As his mission begins, Ichika rises to his final frontier...