On Naho Takamiya's first day of her second year at high school, the start is uneasy and deeply unsettling silence. She wakes up late and finds a letter tucked in her backpack, addressed to her. The note turns out to be from herself—ten years ahead, handwritten envelope! Initially, Naho doubts the message; but after witnessing several predicted events and a chill down her spine, she confirms that the letter comes from her 26‑year‑old self. The correspondence reveals a future remorse and the writer wishes her younger self could amend past errors and heartbreaks that haunt. It also cautions Naho to watch closely the new transfer, Kakeru Naruse whose presence feels familiar. She must be cautious in decisions involving him because he will not appear in the future and his absence leave a void. Armed with this guidance, Naho now can shield Kakeru before she regrets it again her path stays true.
