Reiraku

are the visualization of Reiryoku into threads which spiritually aware people can follow. According to Rukia Kuchiki, this is a high-level technique. When Uryu Ishida uses Reiraku, before the start of his and Ichigo's competition, he states it's "something that compresses and visualizes the spiritual auras in the atmosphere" and that only upper level Shinigami can visualize and touch them. To the user of the technique, a Shinigami's spirit coil appears to be red, while that of other beings appear to be white. Ichigo Kurosaki used this technique for the first time when searching for a Plus hiding inside a pet bird, and later when he had to journey to his "inner world" (the depths of his soul) in order to find his Shinigami powers, which were hidden in one box among millions, the boxes representing the humanity of his soul.

Reiraku Users
All Shinigami and Quincy have access to the Reiraku technique. However, the only two people ever seen using it are Ichigo and Uryū.