Spirit Threads

Spirit threads or Reiraku are the visualization of Spiritual Energy into threads which a spiritually aware person can follow. Rukia Kuchiki says this is a high-level technique. Shinigami have a red spirit thread, while other people have white. Ichigo Kurosaki was able to see spirit threads for the first time, when he had to journey to his "inner world" (the depths of his soul) and learn the name of his zanpakutō.