Shakugan no Shana T3 E1 – 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.
Shakugan no Shana
The world has become a slaughtering ground for the Crimson Denizens, mysterious beings from a parallel universe who thrive on the life energy of humans. These merciless murderers only leave behind scant remainders of souls called "Torches," which are mere residues that will eventually be destroyed, along with the very fact of the victims' existence from the minds of the living. In an ambitious endeavor to put an end to this invisible, hungry massacre, warriors called Flame Hazes relentlessly fight these monsters. One fateful day, Yuuji Sakai ceases to be a regular high schooler—he becomes trapped in a crevice of time and is suddenly attacked by a Denizen. Coming to his rescue just in the nick of time is a nameless hunter who seems no different from an ordinary young girl except for her blazing eyes and burning crimson hair. However, before Yuuji can learn anything more about his situation, he discovers that he has already been reduced to a Torch—merely a scrap of memory waiting to be extinguished.