Upon receiving an email from Agil containing a picture from Alfheim Online, Kazuto (Kirito) immediately went to visit Andrew (Agil) at the Dicey Cafe. Andrew told him about the girl, who looked very similar to Asuna, who was trapped inside a birdcage on top of the World Tree. Kazuto also noticed that the game was designed by RECTO Progress Inc., the same company Sugou worked for who was also in charge of the SAO servers. Upon entering the ALO, Kirito’s suspicions were confirmed when he reunited with his “daughter”, Yui.
I thought it was a lovely scene to see Kirito reunite with Yui, even though ALO was a weird half season for me. Thanks to Jennifer for sending this in!
Source: SAO 52pk