An incident in which the full moon was stolen from the sky.
Reimu and Yukari, Marisa and Alice, Remilia and Sakuya, and Yuyuko and Youmu each departed to investigate.
The Border Team and the Magic Team both halted the night so they could investigate the missing moon. In turn, the Scarlet team and the Ghost team investigated the endless night caused by the first two teams.
Eventually, the moon was recovered and everything was resolved.
Known as the Missing Moon incident, and as the Endless Night incident.