Curses are relatively easy to handle, because Reiger himself can use multiple techniques. As long as you avoid using representative techniques like [Limitless Jujutsu], [Ten Shadow Techniques], [Red Blood Manipulation], or [Curse Speech], then using other techniques probably won't expose Reiger's identity.
But magic power is different.
Everyone's magic power is unique.
That's why, when the residue of magic power is left behind, mages can often discern the identity of those who appeared at the scene and used jujutsu through the "taste" of the residue.
Geto Suguru intentionally lifted the control of [Curse Spirit Manipulation Technique] over curse spirits during the Capital City sister school exchange event to cover up any residue his own magic power might have left.
In such a scenario, once Reiger uses a technique and exposes his own magic power, Geto Suguru will be able to recognize Reiger's identity by sensing the residue.
