Mirai is a supernatural entity from the manga and anime series Toilet-Bound Hanako-kun. She is one of the Three Clock Keepers, a group that serves as the first of the Seven Wonders of Kamome Academy, and holds the role of the keeper of the future. She does not appear to have a real name; the character Akane Aoi gave her the name Mirai, which means future in Japanese.

In terms of background, Mirai is a childlike supernatural who, along with Kako, the keeper of the past, and Akane Aoi, the keeper of the present, maintains the flow of time within the school. Her origin is not deeply explored, but she exists as a personification of the future itself, giving her a fundamental connection to the passage of time.

Personality-wise, Mirai is mischievous, cheerful, and highly energetic. She exhibits a playful and sometimes reckless demeanor, often acting without thinking about the consequences of her actions. She speaks in a childlike manner, frequently referring to herself in the third person, and has a noticeable fondness for treats and sweets. According to Akane, she is dimwitted, which contributes to the chaos she can inadvertently cause.

Mirai's primary motivation appears to be the pursuit of amusement and enjoyment. She finds joy in using her powers to cause changes and disruptions, and she seems to consider elderly or aged individuals cool or interesting. Her actions are driven by a simple, childlike curiosity rather than malice, though her lack of foresight can lead to dangerous situations.

Within the story, Mirai serves as an antagonist during the Clock Keepers arc. When the clock that controls time at the academy breaks down, she escapes and begins accelerating time on anything she touches, causing chaos across the school. Her role involves testing the main characters, Nene Yashiro, Kou Minamoto, and Hanako, as they attempt to restore order and repair the clock's function. She is a source of both comedic and tense moments due to her unpredictable nature.

Key relationships include her fellow Clock Keepers. She is partnered with Kako, an elderly supernatural who controls the past, and works alongside Akane Aoi, who controls the present. Her interactions with Hanako, Nene, and Kou are primarily adversarial, as they try to stop her rampage. She is notably swift and difficult to capture; even when Kou manages to catch her, she uses her powers to escape. There is a specific concern that her time manipulation could be especially dangerous for Nene, as Hanako notes that Nene does not have a distant future, making the effects of accelerated time unpredictable for her.

Mirai's development as a character is limited within the narrative, as she primarily functions as a force of nature rather than a figure who undergoes personal growth. She remains largely static, defined by her unshakeable childishness and her role as a chaotic element that the protagonists must manage.

Mirai's notable ability is the power to accelerate the passage of time for anything she touches. This can cause objects to decay rapidly, window glass to shatter, and potted plants to grow into full-size trees in moments. When applied to living beings, she can instantly age students into elderly people, though their bone structure and facial features remain unchanged, suggesting a superficial effect. Because she is still a child in demeanor, her control over this ability is inconsistent, and her careless usage can easily lead to widespread disorder if she is not closely supervised.