Tenkei Iwafune, formerly Seigo Ootori, served as the Sixth Gray King and founded the Cathedral clan. Cathedral rose to become the second most powerful clan after the Gold Clan, earning him considerable respect. The clan's final mission aimed to prevent the Kagutsu Crater incident, but the effort failed catastrophically, killing all members except Iwafune. Scouring the crater's aftermath, he discovered Nagare Hisui critically injured, a rock piercing his heart. Nagare had survived through the activation of his powers as the newly chosen Green King. This led Iwafune to conclude that widespread access to such powers could have prevented the mass casualties. Profoundly affected by the disaster, he discarded his identity as Seigo Ootori, adopted the name Tenkei Iwafune, and vanished. He views his former self as dead, openly calls himself a coward, and remains indifferent to insults about his choices. His disillusionment extends to the Dresden Slate, which he sees as a manipulative force reducing Kings to "playthings." He advocates for life moderation, believing high ideals inevitably lead to crushing disappointment. Iwafune eventually aligned with Nagare Hisui and the Green Clan JUNGLE, acting as a father figure. Despite his status as a King, he displays a laid-back and unremarkable demeanor, often laughing off informal treatment from younger clansmen. He drinks frequently and handles domestic chores at their base, including vacuuming and enforcing rules like limiting Sukuna Gojo's gaming time. This domesticity contrasts sharply with his willingness to use lethal force against perceived obstacles, even children, as demonstrated when he fired at Anna Kushina. As the Gray King, his aura generates dense fog, providing an "ultimate defense" by obscuring vision and confusing enemies. He notably deployed this during JUNGLE's assault on Mihashira Tower to aid Nagare's infiltration. He channels his aura through firearms to enhance bullets for combat. Historically a pacifist, the Kagutsu Crater incident shifted his perspective, leading him to engage in combat pragmatically. His motivations intertwine profound regret over failing to protect Cathedral with a desire to prevent future tragedies. He supports Nagare's goal of unleashing the Dresden Slate's power to humanity, believing universal access to abilities would eliminate dependence on Kings and avert disasters like Kagutsu Crater. During the climax at Mihashira Tower, he encouraged Nagare's confrontation with the other Kings and provided tactical support. Following Nagare's death after the Slate's destruction nullified the powers sustaining him, Iwafune chose to die alongside him. In the spin-off "The Idol K," he appears alongside Nagare as part of an idol production team.