Sword Art Online - S1: Episode 22
Leafa tries to stop kirito as he dashes for the lower branches of the world tree only to be stopped by the new barrier that had been “patched” into the game earlier. Kirito then finds a card that is dropped down by Asuna due to hearing Yui calling to her “Momma!”. Kirito then has Yui identify the card as a Sys-Admin pass code card for use on a GM console, and makes a mad dash for the opening gate to the world tree quest. Kirito makes a heroic fight to reach the portal at the top of the chamber, but is diced to bits before reaching it. Kirito dies from the hundreds of spawned “Guardians”, but is saved by Leafa. Upon being revived by Leafa, Kirito states he can not stop fighting until Asuna is safe, which at that time Leafa learns that Kirito-Kun is actually her brother in real life. Or so it seems, as in the real world after they both logoff that they are not actually blood related brother and sister.