Master Swordsman: Due to training and refining his swordsmanship skill for almost 500 years and getting a major boost to his physical capabilities, Kokushibo has become one of the most powerful and skilled swordsmen to have ever lived. As a Demon Slayer in the Golden Age of Demon Slayers, his swordsmanship was already outstanding as he learnt many of his techniques from Yoriichi himself. According to himself, his techniques were so refined and legendary that they have no hopes of it being passed down for future generations. [58] Kokushibo's fear of defeat stems from his inferiority complex and desire for strength. This fear causes him to become increasingly aggressive and desperate in battle, relying on his demon powers. However, as he faces off against the Hashira, Kokushibo realizes the heavy cost of his pursuit of strength. He becomes a grotesque monster, far from his idealized vision of becoming the strongest samurai like his brother, highlighting how his ambitions and resentment have twisted him. Demon Slayer Mark: Kokushibo awakened his mark when he trained under Yoriichi. [33] The Demon Slayer Mark drastically improves the abilities of an individual, making them much stronger and faster than what they can achieve normally, though at the cost of being cursed to die at the age of 25. However, by turning into a demon and gaining immortality, Kokushibo is no longer bound by the curse.

Sixteenth Form: Moonbow, Half Moon ( 拾 ( じゅう ) 陸 ( ろく ) ノ 型 ( かた ) 月虹 ( げっこう ) ・ 片 ( かた ) 割 ( わ ) れ 月 ( づき ) , Jū Roku no kata: Gekkō - Katawaredzuki ?) [21] - Using his altered katana, Kokushibo swings upward, sending six curved slashes crashing down several meters in front of him, powerful enough to leave craters in their wake.All in all, Kokushibo's defeat required the combined efforts of three powerful Marked Hashira (two of which awakened the Transparent World) with Bright Red Blades, a Demon Slayer capable of using Blood Demon Arts, and even then, the battle was narrowly won and cost the Demon Slayers' two lives, a feat that truly exemplifies the might of Upper Rank One. Ninth Form: Waning Moonswaths ( 玖 ( く ) ノ 型 ( かた ) 降 ( くだ ) り 月 ( づき ) ・ 連 ( れん ) 面 ( めん ) , Ku no kata: Kudaridzuki - Renmen ?) [74] - Using his altered katana, Kokushibo performs multiple curved slashes, all in close proximity, that leave numerous crescent moon blades along its path. It is revealed that as a human, Kokushibo harbored an immense sense of envy towards his younger twin brother for his natural talent and incredible abilities. These feelings of jealousy and contempt only became stronger upon seeing his brother become a peerless warrior of unmatched caliber among even the Demon Slayer Corps, with none of the Hashira coming close to his level of strength. This envy peaks when he discovers that Yoriichi was still alive and in old age, despite the curse of the Demon Slayer Marks supposedly killing him before he turned 25.

Seventh Form: Mirror of Misfortune, Moonlit ( 漆 ( しち ) ノ 型 ( かた ) 厄 ( やっ ) 鏡 ( きょう ) ・ 月 ( づき ) 映 ( ば ) え , Shichi no kata: Yakkyō - Dzukibae ?) [73] - Using his altered katana, Kokushibo performs a frontal crescent-shaped slash that unleashes numerous straight and curved slashes that expand outward.As the highest ranking member of the Twelve Kizuki, Kokushibo is an extraordinarily powerful demon, second only to the Demon King Muzan Kibutsuji himself. He has battled countless Demon Slayers and has amassed vast experience and knowledge over his near 500-year long life. His abilities have been refined to the highest level as he is not only a master of Total Concentration Breathing, but also a marked individual who has gained access to the Transparent World, as well as the demon that possesses the highest concentration of Muzan's blood in the organization. [12]