This technique is the ultimate jutsu of Josho Adashino, and the culmination of his Rashomon-based techniques. It combines his mastery of Rashomon variants with Huginn and Muninn, the jutsu he created which use the energy within the gate, and utilizes them together for an awe-inspiring jutsu. He uses the material of the Rashomon Gate itself to create a giant creature, in the form of one of the Bijū, and uses the energy from within the gate to give it energy symmetrical to that of the original beast. He even gives it energy that mimics the beast's life force near perfectly, to the point where the malicious intent can be felt. Despite this, he is in control, though it may react to its surroundings if he does not rein it in completely. It has two forms, the more physical, solid form representing this side of the Rashomon Gate, and the darker, more spiritual form, considerably more powerful, representing the far side of the Rashomon Gate. This form of Rashomon can be used to fuel other Rashomon-based techniques.
Despite the name, this jutsu has been shown to be capable of mimicking things other than Biju, such as Susano'o, another physical apparition of chakra.
Rashomon: Bijū is the only technique to utilize the Raven hand sign, and in fact utilizes a Double Raven, one performed with each hand at the same time.