In the game series .hack//Roots, Haseo is a newbie player who joins an online world known as The World R2. He is initially an outcast in real life and struggles with social interactions. Upon logging into The World R2, he is attacked by PKs (Player Killers) but is rescued by Ovan, the leader of the Twilight Brigade. Haseo then joins the group to learn more about Ovan. However, after Ovan disappears for an extended period, the Twilight Brigade disbands and Shino is killed by Tri-Edge. Driven by a desire to save Shino, Haseo becomes obsessed with gaining power and embarks on a journey into the Forest of Pain, where he transforms his PC body after confronting another AI named Harald. At this point, level 133 and equipped with powerful weapons, Haseo becomes known as the Terror of Death, a PKK (Player Killer Killer) who hunts down PKs. He demands information on Tri-Edge from any players he encounters but kills them if they fail to provide useful information. The name "Terror of Death" is given to him by other players. Around this time, Ovan returns and informs Haseo that Tri-Edge will reappear at the Hidden Forbidden Holy Ground. However, Haseo is Data-Drained upon attempting to defeat Tri-Edge and wakes up as a level 1 character with no items or contact information. Ephitaph users, a select few with Avatars used to fight against Tri-Edge and other threats, use these creatures to delete bugs called AIDA from infected players using the special move "data drain." While it is never officially stated whether they are the same person or not, Haseo shares a real name and age close to that of Sora from .hack//sign as well as a connection to skeith.