The ability allows the player to replicate the abilities of the opponents that have been fought, and treat as their own. With Usamimi, the player's goal is to become the strongest in Academy City. However, due to the fact that it can also replicate magic, it is seen as a violation of the treaty between the magic and science sides, making the player and Usamimi the target of assassins from both factions.
Although how the ability is uncertain, Usamimi however seems to understand it enough for her to be able to hone the player's ability since meeting with her.
Due to the fact that the player is unfamiliar to battle, Usamimi gives the player the Booster, something of her own invention, and suggests to the player to use it to be able reinforce his ability. In the first battle, the player is able to replicate Misaka Mikoto's Railgun, and apparently not only limited to esper abilities as Stiyl Magnus' Flame Sword can also be replicated. Moreover, the acquired ability can also be developed by the experience gained by the player. The replicated ability apparently is not inferior to the original, as demonstrated by the player using the Railgun to destroy a building.
When the player does battle with Usamimi, she references Fantasy Shadow Copy (空想写影 Kūsō Shaei?), apparently referencing the player's ability. In the event "Fallen Angel Fuse=KAZAKIRI," the 0930 incident is reproduced through the use of Phenomenon of the Past (過去の現象 Kako no Genshō?), making it seem that it does not only replicate powers but also major events in the timeline, though the current relationship between his ability and time, and if it can interfere with the timeline is unknown.
- ↑ 1.0 1.1 Imagine Shadow from the Toaru Majutsu no Index @wiki (Japanese). Retrieved on 13/1/16