After the victim is trapped in Haku's ice mirrors, he attacks the victim in high speed like he does with the Demonic Mirroring Ice Crystals technique. During this, the dome starts to float in the air. After that, a clash of blue light explodes inside the dome, damaging the victim greatly. Right before this happens, Haku escapes at the last second, to prevent harm to himself. The mirrors then shatter into a million ice pieces.
The full name of this technique is "Secret Technique: Demonic Mirroring Ice Murder" (秘術・魔鏡氷殺, Hijutsu: Makyō Hyōsatsu).