Mitsurugi Hanagata is a prominent supporting character whose introduction inadvertently sets the series' plot into motion. He is the heir to the wealthy and influential Hanagata Trust, a financial organization with interests across the planet. The story begins when his reckless driving causes him to collide with the protagonist, Otaru Mamiya, an accident that ultimately leads to Otaru awakening the first of the special marionettes.

In terms of personality, Hanagata is a highly flamboyant and dramatic individual who thrives on attention. He is often portrayed as a spoiled young man from a privileged background, and his behavior is typically over-the-top, making him a primary source of comic relief within the narrative. His defining characteristic is his passionate and unwavering romantic obsession with Otaru Mamiya, whom he views as the object of his genuine affection and persistently tries to win over. Despite this obsession often being played for laughs, his feelings are portrayed as true and sincere.

Hanagata's primary motivation throughout the series is his desire to be close to Otaru and to turn Otaru's affection away from the three marionettes, Lime, Cherry, and Bloodberry, whom he initially views as unnatural rivals. His role in the story is largely that of an antagonist and a comedic foil to the main household. After his family mansion is destroyed by a fire, he moves into the apartment next door to Otaru, making himself a constant, albeit often unwelcome, presence in their lives. His persistent schemes to get Otaru's attention or to prove his own worth frequently end in failure and physical comedy, often resulting in him being sent flying through the air or knocked unconscious, yet he always recovers with remarkable resilience.

Hanagata's key relationships are centered on Otaru and the three marionettes. His feelings for Otaru are the driving force of his actions. Over time, his rivalry with Lime, Cherry, and Bloodberry evolves into a grudging respect, especially after Lime saves his younger brother, Yumeji, from the fire that destroyed his home. He also has a protective relationship with his young brother, Yumeji Hanagata, and his actions are sometimes guided by a desire to keep him safe. Despite his antagonistic role, Hanagata experiences significant character development. As the story progresses and serious crises arise, he demonstrates that his care for Otaru is not purely selfish. Notably, when Lime’s maiden circuit, the source of her heart, is stolen, Hanagata chooses to help in the desperate search for it rather than using the situation to his own advantage, thereby placing Otaru's happiness above his own. This marks a maturation from a purely selfish individual to one capable of genuine selflessness for the sake of a loved one.

Regarding abilities, Hanagata possesses no special powers or combat skills. His most notable traits are extreme persistence, stubbornness, and a seemingly superhuman level of resilience that allows him to survive physical trauma that would be fatal to a normal person, such as surviving falls from great heights or being thrown at incredible speeds. These abilities are a function of his role as a comedic character, ensuring he can be the constant target of slapstick violence without serious consequence.