Kanon Seena, a human student from the real world, belongs to the Student Council at St. Luminous College. She possesses red or orange hair, light brown eyes, and stands 157 cm (5'2") tall. Her standard attire is a school uniform comprising a jacket, tie, plaid mini skirt, knee-high stockings, and boots, frequently accessorized with a hat featuring the school crest.

Transported to the fantasy realm of End Earth alongside classmate Kaito Kiriya shortly after Souma Akizuki and Touka Kureha's displacement, she co-founds the independent mercenary group the Luminous Knights, leading it while Kiriya serves as primary knight. She exhibits leadership and combat proficiency, demonstrating notable skill in fencing.

Her combat abilities focus on supporting Kiriya, allowing him to manifest her heart as the unique Gun Sword Blade Cannon weapon. This empowers his role as a Soul Blader, reflecting her loyalty and dedication to the group. Amid conflicts involving factions like Baelgard and the Weissritter, she remains with the Luminous Knights, engaging in key battles and strategic efforts.

She has a younger brother named Rage. Following the resolution of the Holy Grail conflict and the Zeroboros threat, she returns to her original world alongside Kiriya and Kureha, ending her involvement in End Earth.