Junketsu is a major antagonist in the 2013 anime Kill la Kill.
Junketsu's inactive form is that of a white and blue sailor uniform. The design is noticeably more militaristic than normal uniforms, having a high collar, yellow shoulder epaulets and gold adornments along the sides.
In contrast to Senketsu, Junketsu's behavior is aggressively feral and demonic, as Satsuki would put it into heavy restraints when not used. It also appeared to lack the ability to speak, possibly due to it being created without human DNA integrated into its genes, unlike Senketsu. As such, whenever she is using its power, Satsuki would tame the Kamui via the "Life Fiber Override" technique. Befitting to its behavior, it requires more blood than Senketsu, as evidenced by comparing the transformation sequences for both Kamui: Satsuki uses three needles, while Ryūko only uses one to draw blood.
Junketsu was created by the Kiryūin family to be worn by their young daughter Satsuki Kiryūin when she came of age and was referred to as Satsuki's "wedding dress" by her father. At some point later, it was sealed away deep within the Kiryūin manor due to its immense and uncontrollable power.
Years later, Satsuki goes to the mansion to wear Junketsu so she can use its power in her next confrontation with Ryūko, dwarfing her and Senketsu's combined strength as Ryūko had yet to tap into Senketsu's full power out of embarrassment of the Kamui's "exhibitionist" appearance. Even after Ryūko manages to overcome this, Junketsu's strength still beats out Senketsu's. Amused by Ryūko's determination, Satsuki challenges her to defeat all the students in her school to prove herself worthy of facing her and Junketsu's power again.
Later, during the Culture and Sports Festival, Ragyō Kiryūin succeeds in defeating Satsuki and stealing Junketsu from her, claiming that Satsuki is not truly wearing Junketsu and cannot unleash its full power. She then dons the Kamui herself and activates Life Fiber Override, increasing her capabilities to the point that Ragyō can easily sneak behind Ryūko and pull out her heart with her bare hands.
For a time, Junketsu remained in possession of Ragyō until she and Nui later stitched it onto a brainwashed Ryūko, and sending her to destroy the resistance at the S.S. Naked Sun. Fortunately for the heroes, they managed to snap Ryūko from the mental conditioning, causing the horrified and disgusted Ryūko to tear Junketsu into pieces and harming herself in the process (as Junketsu was stitched on her skin during the brainwashing process). Just as Ryūko unceremoniously cut Nui's arms off, Junketsu attempted to crawl away, only to be pinned by Satsuki, firmly telling it to stay put.
The Kamui is retailored back together by Shiro Iori, with a mixture of Ryūko's blood, Satsuki's blood and Senketsu's Life Fibers injected into it. By episode 24, Satsuki gives up Junketsu, allowing Ryūko to fly after Ragyō with Senketsu Kisaragi.