Yui

is the codename of the first version of the «Mental Health - Counselling Program»of «Sword Art Online». She is also Kirito's and Asuna's daughter.

Background
Yui is considered a «Top-down AI» made to monitor the mental health of the players of SAO. She's a pseudo artificial intelligence built from a program atop an existing computer architecture. Top-down AIs can be considered as a cluster of binary.