Miyu is the central human character in the anime She and Her Cat -Everything Flows- and the owner of the black cat Daru. She is a young college student who lives alone with Daru in a small apartment after her childhood friend and former roommate Tomoka moves out to get married. Miyu's background is shaped by loss and transition. Her father died when she was young, and she was raised by her mother in a single-parent household. As a child, Miyu and her mother moved to a new city, where Miyu struggled to make friends and felt isolated. Her mother, concerned about her loneliness, brought home a black kitten named Daru. Miyu initially resented the cat, feeling jealous of the attention her mother gave him and upset when Daru broke a mug that had belonged to her late father. She even attempted to abandon him but could not bring herself to do so. Over time, Daru helped Miyu connect with a classmate named Tomoka, sparking a lasting friendship that became a cornerstone of her childhood.

Miyu's personality is defined by a quiet resilience and a gentle, caring nature. She is often shown smiling despite the stress she carries, though she is prone to anxiety and moments of sadness. She is soft-spoken and introspective, and her emotions are frequently conveyed through small gestures and expressions rather than words. She has a strong sense of independence and pride, as seen when she refuses her mother's offers of financial help after Tomoka moves out, determined to prove to herself and others that she can manage on her own. This drive to be self-sufficient motivates her to search for work while continuing her studies, even when the process is discouraging and lonely.

Miyu's role in the story is to be the human counterpart to Daru, the feline narrator. The anime is told entirely from Daru's perspective, so Miyu's inner thoughts and feelings are never directly voiced. Instead, the audience understands her through Daru's observations of her actions, her routines, and the subtle shifts in her mood. She serves as the emotional anchor of the narrative, representing the universal experiences of grief, solitude, the struggle for independence, and the quiet comfort of companionship.

Her key relationships are with Daru and Tomoka. Daru is her constant companion from childhood through young adulthood. Despite their inability to communicate verbally, the bond between them is deep and mutual. Miyu cares for Daru's daily needs, talks to him, and finds emotional solace in his presence during difficult times. Daru, in turn, loves her unconditionally and tries to comfort her in his own way. Tomoka is Miyu's closest human friend, who helped her come out of her shell as a child and remained a steady presence in her life until she moved away to marry. Their friendship is one of the few social connections Miyu maintains, and Tomoka's departure marks a turning point that forces Miyu to face adulthood more directly. Miyu also has a relationship with her mother, which is warm but marked by Miyu's desire to assert her independence. Later in the story, after Daru's death, Miyu encounters and takes in a stray white cat named Chobi, beginning a new chapter of companionship.

Miyu undergoes significant development over the course of the anime. She transitions from a child who resists change and struggles with loneliness into a young adult who learns to navigate life's challenges on her own terms. She grows through loss, learns to accept help when needed, and ultimately finds the strength to open her heart to a new companion after Daru passes away. Her journey reflects the cycle of life, love, and letting go.

Miyu does not possess any supernatural or extraordinary abilities. Her notable qualities are her emotional perceptiveness, her capacity for quiet endurance, and her ability to find comfort and connection in the simple act of caring for another being. She is a grounding presence whose strength is gentle rather than loud, and her story is one of finding meaning in the ordinary moments of daily life shared with a beloved pet.