Shakugan no Shana - Season 3 Episode 1 Lost Existence

Yuji's existence has disappeared on Christmas Eve after the events of Statue of Pride. Like a disappearance of a torch, all those who aren't engaged in the World of Guze have forgotten him including his closest friends and families. Shana and Kazumi still believe that Yuji exists due to the fact that their letters given to Yuji haven't disappeared. However it is shown that Yuji still exists but makes a contract with a Guze no Tomogara and takes the Serei-dens throne as the new leader of Bal Masque.