Yui Hahaoya
Yui Hahaoya, later known as Model 2-E, is a player in The Murderverse.
Background
Originally a scientist working at MAE, Yui would end up creating Metabomb, making her responsible for the events of .EXE ~ A Virus Containment Game. After the creation of Metabomb, Yui would end up wiping her mind, reducing her to a child in an adult's body.
.EXE ~ A Virus Containment Game 2
Yui is first introduced in .EXE ~ A Virus Containment Game as a childish spirit possessing a serial killer known as Jocelyn, with the two collectively being referred to as Jui. However, shortly after Jocelyn/Yui were executed, this "Yui" (which would eventually be known only as Jui, regardless of if she was possessing Jocelyn or not) was revealed through a video recording to be what's left of the "real" Yui who created Metabomb.
Your Final Frontier 3
Shortly before wiping her mind, Yui would upload a copy of her original mind into a robot known as "Model 2-E". 2-E would then end up captured by the Alliance to take place in Your Final Frontier 3, where she served as the Watcher and survived up to the end.