Asuka Tennōji is the central protagonist of Z/X Ignition, a young man whose ordinary life is upended when he becomes entangled in a conflict that spans five parallel worlds. He is a second-year student at Seiryuu Private High School in Kobe, where he lives in the boys' dormitory and works a part-time job at a café called Cafe Broccolo. Originally from Osaka, Asuka is sixteen years old and has a family history marked by hardship; his father passed away at a young age, and his mother became ill from overwork, leaving her hospitalized and requiring Asuka to become self-sufficient from an early age. He has a close relationship with his older brother, Yamato, who works overseas.

Asuka possesses a striking and handsome appearance, but his personality is that of a comedic, lighthearted, and somewhat goofy individual. He is fundamentally warm-hearted, cheerful, and possesses a strong sense of justice, believing wholeheartedly in the potential for peaceful coexistence between humans and the Z/X. This inherent brightness and personal charm naturally attract people to him, expanding his circle of friends and allies. He is a fan of comedy and claims to know a million jokes, though his easygoing and often oblivious nature has historically made it difficult for him to find a girlfriend. Despite his comic demeanor, he has developed a practical and responsible side from caring for his family, becoming highly skilled at housework, particularly sewing, to the point where he can create costumes on his own.

His journey into the central conflict begins when he rescues an injured angel named Feliti, an act that leads to him receiving a card device and becoming her partner. While other main characters entered the battle with specific goals, Asuka is described as having gotten involved purely by accident. His primary motivation throughout the story is not personal revenge or ambition but a sincere desire to protect others and foster understanding between humans and the Z/X. This optimistic and compassionate outlook makes him the driving force of the narrative, as he faces every challenge with an upbeat spirit.

Within the story, Asuka serves as a magnetic figure around whom other key characters gather. His most significant relationship is with his partner, Feliti, a proud angel from the White World. Their bond develops from initial friction into a deep partnership, with Feliti often reacting jealously to Asuka's kindness toward other girls. He also forms crucial alliances with other Z/X players, including the revenge-driven Ayase Kamiyugi and the sickly Azumi Kagamihara. Despite his obliviousness to romance, he forms a close friendship with his childhood friend Aina Mikage. Throughout the series, Asuka remains a steadfast Nice Guy, using his natural charisma to unite others against common threats like the entity known as Audium. His development is subtle but significant; while he starts as a completely ordinary high school student with no combat experience, his experiences in battle help him cultivate a sense of calm and composure in crisis situations, moving beyond just his innate cheerfulness.

Asuka himself does not possess flashy supernatural powers. His notable abilities are his domestic mastery, his communication skills, and his unwavering optimism. However, as a Z/X player, his capability in battle is intrinsically linked to his partner, Feliti, who wields formidable defensive powers and offensive energy attacks. His role is that of a unifier and a catalyst, with the story hinting at a deeper significance to his position. His Dream Key, a special treasure, is associated with the Wheel of Fortune tarot card, symbolizing turning points, encounters, and the sudden changes that constantly define his life.