|“||Oh, Pardon me. I can't quite match faces to names.||”|
Kusabira looks strikingly similar to Zelkova, in both physical appearance and attire, with silver hair, horns and wearing Japanese-style clothing. Her kimono also shows a black pattern that is very reminiscent of AIDA, hinting on her true identity.
As AIDA<Tri-Edge> she was the first AIDA to become hostile toward humans. Its first target was Aina, but its attack was blocked by Ovan who became infected by it instead, transforming him into the very first AIDA-PC. Unlike most other AIDA, <Tri-Edge> is capable of speech by assuming control of Ovan's voice, using it to taunt him over his misdeeds, though due to the nature of their existence the difference between Ovan's actions and Tri Edges are at times blended.
As Kusabira, she is very quiet and polite, but often has issues to remember people, stating she has a problem to "match faces to names". She shows concern and care towards Zelkova, who she calls her "brother", and Ovan, as she was connected to him during a long while infused into his arm as AIDA<Tri-Edge>.
Kusabira is an sentient AI, much like Aura and Zelkova, but carries the remnants of AIDA. She appears in the system after Ovan successfully purges most of AIDA from existence and the internet using Corbenik's Rebirth; with however, rhw leftover data of Tri-Edge (AIDA) remaining and taking a form of its own, giving birth to Kusabira.
Residing inside of Ovan, Tri-Edge was fairly quiet. Except in a few cases where it broke free and created Signs Ovan was able to keep it mostly under control. However, when Ovan was captured by Naobi and Ender his character data was put under a complete scan. The scan caused Tri-Edge to awaken and destroy the containment area, allowing Ovan to escape. Fleeing to the Hulle Granz Cathedral Ovan tried to collect himself, but before he could get Tri-Edge back under control Shino appeared. Sensing the presence of another PC, Tri-Edge attacked her, turning her into a Lost One. Grief-stricken, Ovan fled the area and hid within the system for several months.
Attracted by Tri-Edge's data, Azure Flame Kite eventually succeeded in hunting down Ovan and attempted to defeat him using his Twilight Bracelet. Once again Tri-Edge revealed itself, and destroyed Azure Kite in a single attack. Realizing that this AIDA was something the regular defenders of the system couldn't handle, Ovan decided to place all of his hope on Haseo, the Epitaph User for Skeith. With this plan in mind, Ovan began making plans to strengthen Haseo to the point where he could defeat Tri-Edge.
Unaware that Tri-Edge was actually Ovan, Haseo blindly chased after Azure Kite, who he believed to be the real Tri-Edge. To help Haseo grow stronger Ovan used Tri-Edge's influence over AIDA to supply AIDA to various people within The World R:2, such as Sakaki, the Captain of Moon Tree's Second Unit. After Sakaki's attempted coup d'état of Moon Tree; Haseo, Pi, and Atoli pursued him to Briona Gwydion where they were able to successfully defeat him. Azure Kite, accompanied by Azure Balmung and Azure Orca also came after Sakaki, but Ovan destroyed them using Tri-Edge's power. Taking Azure Kite's severed arm he entered Briona Gwydion himself, and went to talk with Haseo.
However, during their conversation Tri-Edge began to activate. Realizing he couldn't contain it Ovan revealed himself to Haseo, and easily PKed both Pi and Atoli. Fleeing to Inverted City Megin Fi, he was pursued by an enraged Haseo. The two began to fight, first as normal PCs, and then using their respective Avatars, Corbenik and Skeith. Though Skeith emerged victorious in the fight, its power was still not enough to cleanse Ovan of Tri-Edge. Soon after the fight Ovan reappeared before Haseo, once again telling him to grow stronger.
Later, Tri-Edge is once again revealed as Haseo fights him in The Creator's Room. After Haseo defeated Corbenik with a fully awakened Skeith, Ovan used the ability of his Avatar, the "Rebirth", to reinitialize all of network, eradicating most of the aggressive AIDA, seemingly including Tri-Edge.
She, alongside with other AIDAs debate on wheather or not they should coexist with humankind. Most of her comrades consider her judgement to be viased due to her having spend time with a human. Eventualy the other AIDAs concede and decide to make a decision based on the results of Haseo´s quest to rescue Ovan.
Kusabira makes her first "physical" appearance in Volume 4, presenting herself to Haseo. Calling herself "Zelkova's 'sister", she asks his help to save Zelkova from a vicious monster known as Shadow Vegalta, which seeks to consume anything that is outside of the game specs. The creature attacked Zelkova in the Net Slum Tartarga, swallowing him and slowly consuming his data. Kusabira also states that she can help save Ovan in Q'ha Holme, but only if this monster is defeated.
Haseo manages to defeat Shadow Vegalta, only for it to retreat and regenerate. With the help of Pi, Haseo enters the Net Slum Tartarga again via Area Hacking, where she entrusts him with a program that can prevent Shadow Vegalta from regenerating. Together they destroy the monster for good, and rescue Zelkova, who then proceeds to help Haseo by giving him back Skeith, this time successfully imbuing his PC with the power of all the Epitaphs, giving birth to his 5th Form.
Using this new power, Haseo rescues Ovan from his ice cage, however, he remains unconscious. It is then revealed that after Ovan successfully purged all the existence of AIDA from the internet using Corbenik's Rebirth, a leftover data of Tri-Edge (AIDA) remained, taking a form of its own and giving birth to Kusabira, a female AI which carried the remnants of AIDA. Kusabira then merges with Ovan, waking him from his coma.
- "Yes, that's right...I'm the one who made your sister a Lost One."
- — AIDA<Tri-Edge> speaking through Ovan —