Kazuki Yotsuga is the central protagonist of the anime Dual! Parallel Trouble Adventure. He is initially presented as a shy, quiet, and somewhat awkward high school student who feels like an outsider among his peers. This social isolation stems from a singular, unusual trait: he periodically experiences disturbingly realistic visions of massive giant robots battling each other in the streets of his city. These hallucinations cause him to react to dangers that others cannot see, leading classmates to regard him as strange and leading him to document his experiences on a personal website.

His background is that of an ordinary teenager until his life is upended by Mitsuki Sanada, the most popular girl in his school. Having read about his visions online, Mitsuki brings Kazuki to meet her father, Dr. Ken Sanada, a scientist researching parallel worlds who theorizes that Kazuki is actually witnessing events in an alternate dimension. An accident during one of Dr. Sanada’s experiments transports Kazuki and Mitsuki to that very parallel reality where he was never born. This new world is embroiled in a conflict between the Earth Defense Force and the conquering Rara Army, fought with the very real versions of the giant robots from his visions.

In this unfamiliar and dangerous world, Kazuki discovers his unique role. When he accidentally climbs into the cockpit of a white Core Robot during a skirmish, he demonstrates incredible, instinctive piloting skill. This talent leads to him becoming the new pilot of the robot, which he knows as Hartzenen, and being recruited into the Earth Defense Force. His role in the story is that of an accidental hero, a seemingly ordinary boy who is uniquely suited to pilot the advanced mecha and is soon caught in a struggle to prevent the destruction of both his world and the parallel one.

Kazuki’s personality evolves subtly through his interactions with the people he meets. While he remains the quiet center of the narrative, he shows a growing sense of responsibility and selflessness. His inherent kindness acts as a catalyst for those around him. For instance, he rescues the injured original pilot, Yayoi Schwael, who later becomes a housemate and commander. He also forms a profound bond with D, a mysterious young bioroid who initially acts mechanically but begins to develop human emotions through her connection with Kazuki. He is later captured by the Rara Army and falls for their poster girl, Ms. Ra, who is actually the parallel world’s sweet and gentle counterpart to the more aggressive Mitsuki Sanada. This alternate Mitsuki defects from her army to help Kazuki escape and joins his growing household. Back in his original world, the headstrong Mitsuki Sanada harbors hidden feelings for him, which she often masks by giving him a hard time.

A major turning point in his development occurs when he is badly injured in an attack. In this moment of crisis, he subconsciously awakens Zinv, an ancient, incredibly powerful original Core Robot. It is ultimately revealed that Zinv is not merely a machine but Kazuki’s own counterpart in the parallel world. The increasing dimensional travel begins to break down the barriers between the two realities, threatening to annihilate both. The only solution is to destroy the entity causing the paradox, which is Zinv. Kazuki agrees to this sacrifice, demonstrating his willingness to put the needs of two universes above his own power and existence.

When Zinv is destroyed, Kazuki’s deep-seated desire for all his friends to stay together results in the creation of a third, stable world that merges elements from the two realities. Following the crisis, he lives with Dr. Sanada and all the young women he befriended, now a more experienced and connected individual. It is later discovered that Zinv survived the destruction and regenerated, eventually returning to Kazuki, who then uses the sentient robot as a means to explore space.

Kazuki’s most notable ability is his extraordinary, instinctive talent for piloting the Core Robots, a skill that seems to defy logical explanation and sets him apart from all other male pilots. His connection to Zinv is particularly deep, as the robot is a part of his parallel self. Through Zinv, Kazuki can access immense gravimetric powers, including generating destructive energy projectiles and even manifesting Light Hawk Wings, a defensive and offensive ability of immense power. Beyond his piloting prowess, his primary ability is his sincere and kind nature, which draws people to him and inspires loyalty and change in them, from the emotionally detached D to the enemy soldier Mitsuki Rara.