Takashi becomes Ami's stepbrother five years before the main narrative when their parents remarry. Frequent parental absence due to work forces them together in their shared home, forging a deep and unique bond where Takashi becomes irreplaceable in Ami's life.

A talented guitarist, Takashi performs with a band, a pursuit that garners him popularity. He demonstrates a strong protective instinct towards Ami. This surfaces visibly when he arrives at her school to deliver concert tickets and witnesses her being bullied by classmates like Satomi.

Over time, Ami develops romantic feelings for Takashi, emotions that transcend sibling affection and create significant internal conflict. This leads to a complex shift in their relationship, intensifying the tension between their deepening connection and societal expectations of their sibling status. Their relationship evolves beyond conventional boundaries. However, a specific event referenced as "that day" or "until her fate separates them" introduces a disruption, becoming a turning point. The narrative continues to explore the possibility of a romantic relationship between them amidst these developments.