This article, Blood Transformation Technique, contains content taken directly from our mother site. All credit of such content is reserved the original authors over at Narutopedia, the original article can be read here: "Blood Transformation Technique".
Using the Ketsuryūgan's abilities to manipulate a target's blood, the user can expand the blood in the target's body. Doing so, it will cause the body to morph into a much larger version, effectively disguising the target to be indistinguishable from their true form. By cutting his/her wrists to expel the extra blood, the target will return to their original state.
Kekkei Genkai, Ninjutsu, Dōjutsu