Youjutsu is the Youkai form of spellcraft and is mainly unique to the Youkai. Currently, Kuroka and Sun Wukong are the only Youkai that have used Youjutsu, while Koneko is still training on how to to properly use it.
Youjutsu is an ability unique only to Youkai that allows them to cast both offensive and defensive spells.
Poison Mist Edit
Kuroka demonstrated the ability to produce a poisonous mist that's effective against specific races such as Youkai and Devils, but is ineffective against Dragons or Dragon-type Sacred Gear possessors, such as Issei Hyouodu due to his possession of the Boosted Gear. Kuroka later refined her poison abilitiy, and by using a Bikou as a guinea pig; was able to create a special poison mist which was effective even against Sun Wukong; a former Youkai turned Buddha, even after he dispelled it with his magic.
Youjustsu users have shown the ability to create illusions to confuse and disorient their opponents. Due to their unique nature, a average opponent will be unable to discern the real from the fake due to them taking on the physical appearance of the user.