Senketsu is a Kamui—basically a god-tier outfit that runs on blood. Ryuuko found him as a sailor uniform stashed under her house, and he's been her unlikely partner ever since. The deal with Kamui is straightforward: wear them, and you get godlike power. The catch is they need blood to function, and yeah, the armor form is. skimpy, which Ryuuko finds mortifying every single time.
He can transform into an indestructible suit of armor, which is useful when you're constantly getting into life-or-death battles. His name comes from Ryuuko—"Senketsu" literally means "fresh blood," which tracks given how the whole thing works. Fans often note that despite being, well, a sentient outfit, Senketsu develops a genuine bond with Ryuuko over the course of the series, making him way more than just equipment.
Content compiled by AnimeList.moe from publicly available sources.
