Rashomon is summoned from, but not limited to, Akutagawa's coat, and any other garments he wears. It transforms into an omnivorous, shadow-like black beast. Rashōmon has been shown to be completely adaptable and can switch between offense and defense to suit Akutagawa's needs.
It takes on a form of a shadow-like beast made up of what seems to be dark matter, drawn from inter-dimensional or other similar sources. It can consume anything, even space itself. Once space is split, guns or fire cannot hurt Akutagawa. However, the space rupturing ability needs time to activate, so taking advantage of this can give the enemy a window of opportunity to attack. It can be used for both offense and defense.
- Rashomon: Agito (羅生門・顎, Rashōmon: Agito?, literally "Jaws"): Rashōmon is shaped into the form of a jaw to crush the target.
- Rashomon: Murakumo (羅生門・叢, Rashōmon: Murakumo?, literally "Swarm"): Rashōmon becomes a gigantic clawed appendage which extends from Akutagawa's arm. It can be used to carry out an attack.
- Rashōmon: Higanzakura (羅生門・彼岸桜, Rashōmon: Higanzakura?, literally "Early Blooming Cherry Blossoms"): Rashōmon changes to a tendril-like form, wrapping around the target and lifting him up high in the air. Once at an appropriate height and distance, Rashōmon explodes into several finely-developed flower spikes.
- Rashomon: Sawarabi (羅生門・早蕨, Rashōmon: Sawarabi?, literally "Freshly Budded Bracken"): Several spikes spring up from the ground to thoroughly impale the target.
- Rashomon: Prison Jaws (羅生門・獄門顎, Rashōmon: Gokumon Agito?, literally "Prison Gate Jaws"): A variation of Rashōmon Jaws, considerably smaller in size.
- Rashomon: Spider Thread (羅生門・蜘蛛の糸, Rashōmon: Kumo no Ito?): Rashōmon transforms into thin razor-shaped strings which take a shape similar to that of a spider's web. It can be used as a net to capture the target.
- Rashomon: Endless Jaws (羅生門・連門顎, Rashōmon: Renmon Agito?, literally "Endless Gate Jaws"): Another variation of Rashōmon Jaws. Several Rashōmon Jaws are materialized by Akutagawa to deal with a devastating attack.
- Rashomon: Devoured Space (羅生門・断裂空間, Rashōmon: Danretsu Kūkan?, literally "Space Rupture"): Rashōmon is able to manipulate space to shield Akutagawa, thus, no bullets or any foreign object may hit him. Akutagawa is shown to struggle with his technique initially, as it takes time to activate.
- Rashomon: Demonic Armor (羅生門・天魔纏鎧, Rashōmon: Tenma Tengai?, literally "Demon Wearing Armor"): Akutagawa wraps himself with an exoskeleton-like armor using the black fabric.
- Rashomon: Demonic Jaws (羅生門・天魔顎, Rashōmon: Tenma Agito?): While Akutagawa is wrapped in his exoskeleton Rashomon armor, he directs his power to his arms that take the form and force of Rashomon: Jaws, used mainly for defense.
- Beast Beneath the Moonlight–Rashomon (月下獣羅生門, Gekka-jū Rashōmon?): While Atsushi activates Beast Beneath the Moonlight, he is wrapped by Rashomon.
- Beast Beneath the Moonlight–Rashomon: Toramurakumo (月下獣羅生門・虎叢, Gekka-jū Rashōmon: Tora Murakumo?): Atsushi's tiger claw is wrapped in Rashomon and enhances its offensive power, enough to overwhelm a fully-powered Francis Scott Key Fitzgerald.
- Beast Beneath the Moonlight–Rashomon: Black Tiger's Supreme Claw (月下獣羅生門・黒虎絶爪, Gekka-jū Rashōmon: Kokko Zessō?): Using the tiger's claws that can cut through abilities themselves and Rashomon, Atsushi can stretch out that severed space and cut through physical armor and abilities. As it morphs into a divine blade, Akutagawa claims that no life form can possibly survive from this attack.
Rashomon is based on the real-life Ryunosuke Akutagawa's Rashomon, a short story based on tales from the Konjaku Monogatarishū. The story revolves around a destitute man, who ponders whether to resort to theft in order to survive or to starve to death.