Kaito Fujimura, the eldest son of a wealthy family, lives with the heavy responsibility of taking care of his younger sister, Hina, who is spoiled and always dependent on him. Kaito once met Misaki Aoyama, a simple girl, when they were still children. At that time, Kaito was impressed by Misaki's kindness, but they were separated after that brief encounter. Unexpectedly, they meet again at school when Misaki transfers to the same one. Kaito feels something familiar about Misaki, but he can't fully recall their past meeting.
As time passes, Kaito's feelings for Misaki grow, but a misunderstanding occurs when Kaito accidentally sends a message meant for Hina to Misaki. This complicates their relationship. Kaito is caught between his feelings for Misaki and his obligations to Hina. This story is filled with conflicts, conflicting emotions, and past memories that gradually unfold, bringing them back to a bond they never expected.