TV-Series
Description
Chinatsu Hayase is the younger sister of the protagonist, Masamune Makabe. She is a middle school student, generally considered to be in her early teens, and lives at home with her brother and their mother, Kinue Hayase. Her birthday is given as March 30 in some sources and August 8 in others, leading to some conflicting information about her character profile.

In terms of appearance, Chinatsu has light brown hair, usually styled in a single braid, and brown eyes. She is noted to be of average height for her age and, in a somewhat unusual detail, is actually taller than her mother. She attends a middle school and wears a standard school uniform.

Chinatsu's personality is cheerful, energetic, and often described as a typical little sister. She is talkative, sociable, and not afraid to speak her mind, which can come across as slightly nosy, especially regarding her brother's affairs. Unlike the often tense and dramatic atmosphere surrounding Masamune's quest for revenge, Chinatsu brings a sense of warmth and light-heartedness to the story. She looks up to her older brother and cares about his happiness, even though she does not fully understand the complex and secretive nature of his schemes. Her optimism and straightforward nature contrast sharply with Masamune's more calculating and emotionally guarded demeanor. She is also known to enjoy sweets and simple family meals.

Chinatsu's primary role in the story is as a supporting family member who provides insight into Masamune's home life. Her presence serves to humanize him, showing a softer, more familial side outside of his obsessive revenge plot against Aki Adagaki. She often acts as a source of comic relief, balancing the series' more dramatic moments. For example, she playfully teases Masamune about his love life and has been shown tricking him into building a snowman by calling him an old man. She has also been seen persuading him to invite his girlfriend over for dinner so she can meet her. In another instance, she greets her brother with a jumping kick, suspecting him of going through her laundry.

Chinatsu's key relationships are primarily with her immediate family. She has a close, affectionate bond with her brother, Masamune, whom she calls onii-chan. She can be a source of unwanted advice for him, such as when she suggested he buy a ring or an electric facial device as a White Day gift. She also shares a close-knit relationship with her mother, Kinue, even if she sometimes finds her mother's over-the-top behavior amusing. Chinatsu is apparently unable to tell her mother apart from her cousin, Haruka, leading to some confusion and situations where she has mistaken one for the other.

As a supporting character, Chinatsu does not undergo a significant personal development arc. Her role remains consistent throughout the series, providing stability and a sense of normalcy as the main plot unfolds around her. She is intuitive at times and may realize more about her brother's feelings than he lets on, but she does not become directly involved in his plans. Her motivations are simple and genuine: she wants her brother to be happy and enjoys spending time with her family.

Chinatsu has no notable combat abilities or special skills relevant to the main plot, though she was once an avid reader of a shōjo manga. Her value to the series lies entirely in her function as a grounding, relatable character who represents the uncomplicated family life that Masamune still holds onto.