Decimating Void

When his lover Ishiki Kazeyoshi was murdered by Gin Furyūmonji during their respective battle, Arui's emotions and past trauma overwhelmed himself and his soul so much that his Kekkei Genkai got affected by it. This triggered a radical change within not only Arui's personality, but also his powers and signature ability, the Tatsūna. The trademark blue flames have changed color into a light purple, appearing much more ferocious and stretching up to cover the whole arm, not only Arui's hand. During it's first appearance, Gin described it's aura as something monstrous, something so inhuman that he couldn't believe Arui could hold that sort of power.

Not only did the jutsu change in appearance, it's power also increased dramatically. It was capable of effortlessly breaking Gin's technique, a feat realized by few others before. The general application of the technique has also changed and it is no longer limited to being a short-range thrusting weapon. Arui can now fire devastating waves of energy by swiping his hand in long arcs, each one powerful enough to break through a sturdy  wall. The power and size of each wave differs from the energy that is previously charged within, but the blast used to dispose of Gin took the form of a massive veil of purple energy, similar to Arui's old Kamishini: Severing Waves.

This new technique did incorporate a new backlash, namely that it draws off Arui's life force to achieve it's enormous power, similar to the technique. This was depicted very gruesomely when Arui freed himself of Gin's Dust release technique, where the shattering pillar was accompanied by an eruption of blood on Arui's part. However, Arui seems to have found a way to circumvent this disadvantage, instead using his victim's blood to achieve enough force for the technique.

Darui contemplates that, despite Mutoru and Tatsūna being so much alike, they are entirely opposite of each other, as Tatsūna was born from Arui's desire to protect, and Mutoru from his desire to destroy.