The Ketsuryugan can only be wielded by individuals that possess Chinoike clan blood. The Ketsuryugan’s first made its appearance in episode 484 of Naruto Shippuden and the Sasuke Shinden: Book f Sunrise novel. The canon Dojutsu provides the user with powerful Genjutsu abilities and allow the user to hypnotize their victim. This can be useful to force someone to act against their will physically and to reveal classified information. However, that’s not the most dangerous ability The Ketsuryugan’s user possess.
The Ketsuryugan also allows an individual to manipulate iron and this includes the iron in someone’s blood causing them to boil or explode. As you can imagine, this can cause a lot of problems for the victims of the Ketsuryugan. Furthermore, as we got to see in Naruto Shippuden, the Ketsuryugan is on an even playing field with the Sharingan. With Sasuke Uchiha almost dying against a young child who possessed the Ketsuryugan at the end of Naruto Shippuden. And please do take into account that Sasuke’s Sharingan has evolved into a Mangekeyou Sharingan and he even possessed a Rinnegan at this point.
However, despite the Ketsuryugan’s serious capabilities, the Dojutsu is basically forgotten. The Dojutsu is yet to be mentioned in Boruto Naruto Next Generations, hasn’t appeared in anymore spin-off novels and has only appeared in the Naruto Shippuden: Ultimate Ninja Blazing video game.
This is a technique that can go toe-to-toe with a Sharingan user and we have only every seen it once. This is all very surprising and honestly, this could be a power than be very useful against the god-level threats in Boruto. Hopefully, the Ketsuryugan will not remain forgotten and returns in some aspect in future Naruto and Boruto content.