"Timetable" is a manga series that explores themes of time manipulation, personal growth, and the consequences of altering one's destiny. The narrative centers on Haruto, a high school student who discovers an old, mysterious timetable in his school's library. This timetable allows him to revisit specific moments in his past, offering him the chance to change decisions that have shaped his life. Initially, Haruto uses the timetable to correct minor regrets, such as improving his grades or avoiding embarrassing situations. However, as he delves deeper into its power, he realizes that altering the past has far-reaching and often unintended consequences on his present and future.

The story introduces a supporting cast of characters whose lives become intertwined with Haruto's journey. Among them is Aoi, a classmate who harbors her own regrets and becomes Haruto's confidante as they experiment with the timetable together. Their friendship evolves as they grapple with the moral dilemmas of changing the past. Another key figure is Mr. Takahashi, a teacher who seems to know more about the timetable's origins than he lets on, adding an element of mystery and danger to the narrative.

As Haruto continues to manipulate time, he begins to notice cracks in his reality—subtle inconsistencies and forgotten memories that suggest the timeline is unraveling. The stakes escalate when a rival student, Kaito, discovers the timetable's existence and seeks to exploit it for personal gain, leading to a clash of ideals and a race against time to prevent catastrophic consequences. The story delves into the ethical implications of wielding such power, questioning whether it is possible to achieve true happiness by rewriting the past or if one must learn to accept life's imperfections.

The manga balances its exploration of time travel with a focus on character development, particularly Haruto's growth from a passive individual to someone who takes responsibility for his actions. The narrative structure alternates between moments of introspection and high-stakes drama, creating a compelling blend of emotional depth and suspense. By the conclusion, "Timetable" leaves readers contemplating the fragility of time and the importance of living authentically in the present.