"Surely Someday" is a manga series that revolves around a group of high school students whose lives intertwine through a shared secret and a mysterious game. The protagonist, Kakeru, is a transfer student who becomes entangled in a dangerous and enigmatic challenge known as the "Someday Game." This game, initiated by an anonymous figure, tasks participants with completing specific missions, often involving manipulation, deceit, and moral dilemmas. The stakes are high, as failure to complete the missions results in severe consequences, including public humiliation or even physical harm.

Kakeru is drawn into the game when he receives a cryptic message on his phone, compelling him to participate. As the story progresses, he forms alliances with other students, including the intelligent and resourceful Yuki, the rebellious and outspoken Ryo, and the quiet but observant Aoi. Each character has their own motivations and secrets, which are gradually revealed as the narrative unfolds. The group must navigate a web of lies, betrayal, and shifting loyalties while trying to uncover the identity of the game's mastermind.

The plot is driven by a series of escalating challenges that test the characters' morals, friendships, and resolve. Themes of trust, manipulation, and the consequences of one's actions are central to the story. The tension builds as the characters realize that the game is not merely a schoolyard prank but a carefully orchestrated scheme with far-reaching implications. The narrative explores the psychological toll on the participants, as they struggle to balance their desire to win with their ethical boundaries.

As the story progresses, the group uncovers clues that suggest the game is connected to a tragic event from the past, involving a former student who disappeared under mysterious circumstances. This revelation adds depth to the plot, as the characters begin to question whether the game is a form of revenge, a test of character, or something more sinister. The climax involves a confrontation with the game's orchestrator, leading to a resolution that ties together the various threads of the story while leaving some questions unanswered, adding an element of ambiguity.

"Surely Someday" combines elements of mystery, psychological drama, and suspense, creating a compelling narrative that keeps readers engaged. The characters are well-developed, with distinct personalities and backstories that contribute to the overall tension and complexity of the plot. The manga effectively balances action with introspection, making it a thought-provoking exploration of human behavior under pressure.