Ryuuto Kashima, a melancholic high school student, silently admires his crush, the popular Runa Shirakawa, never daring to hope for reciprocation. Unexpectedly, Ryuuto musters the courage to confess his feelings to Runa, assuming rejection. To his disbelief, she agrees, albeit casually, and even extends an invitation to his surprise. Despite their contrasting personalities, interests, and romantic experiences, their bond deepens each day, marking a unique and meaningful journey of 'firsts' in their evolving relationship.