Kotaro Takidani is one of the three male protagonists in the series, a high school student in his final year navigating a complex web of romantic entanglements. He is introduced as the boyfriend of his classmate Yoko Kishi. Midway through the story, Kotaro experiences a significant change of heart and confides in his friend Yuuichi Takawashi, declaring that he no longer intends to marry Yoko but instead wishes to marry another classmate, Kanami Shiomiya. This decision positions him at the center of a major conflict, as he remains completely unaware that Yoko is pregnant with his child.

His motivations are driven by his evolving feelings for Kanami, which he ultimately chooses to pursue over his existing relationship and the responsibilities he does not yet know he has. His personality is defined by this decisive shift in emotional commitment, revealing a character who can be easily swayed by new attachments and who acts on impulse rather than long-term consideration. As an ordinary high school student in a school drama, Kotaro has no supernatural or extraordinary abilities. His narrative development is entirely relational, revolving around the consequences of his romantic choices and the dramatic irony of his unborn child, which forces him and those around him to face the fallout of his actions.