Naka Ima Shigari is a Kethic discipline that pairs light and dark, the two elements most casters treat as opposites, into one trained craft. Where Midnight Fire turns the dark element into a weapon, this school is built around perception and position. A practitioner bends light to drop out of a guard's eye, throws a false silhouette onto a far wall, pulls a lit room into sudden blindness, or moves through the half-instant when a lamp gutters and the shadow has not yet closed. That half-instant is what the name marks. Naka Ima Shigari is the moment between, the seam where the light has gone and the dark has not yet arrived, and the school teaches its students to live inside it.
The craft is infiltration and killing as much as magic, which is why outsiders call it a ninja school and leave it there. The practitioners would not argue much. Light and dark are routed through the leylines like any Kethic working and cost the caster nothing he does not recover, so a graduate can drill the same techniques night after night without thinning. The discipline is exacting in another way: light bends differently against stone than against water or open air, and a student spends years learning how each surface gives a worker away before learning how to hide from it.
Unlike Midnight Fire, Naka Ima Shigari keeps a real school, a lineage house that takes students young and trains them through to mastery. It hires its graduates out, and it guards its grammar closely. A technique that everyone knows is a technique that no longer hides anything.