"Boku wa Imōto ni Koi o Suru: Secret Sweethearts - Kono Koi wa Himitsu" is a romantic drama anime that explores themes of forbidden love and familial bonds. The story centers on Yori and Iku, twin siblings who share an unusually close relationship. Their bond transcends typical sibling affection, evolving into romantic feelings that they struggle to reconcile with societal norms and personal guilt. The narrative delves into their internal conflicts as they navigate their emotions while attempting to maintain a facade of normalcy in their daily lives.

Yori, the older twin, is protective and deeply devoted to Iku, often prioritizing her well-being above his own. Iku, on the other hand, is more reserved and introspective, grappling with her feelings for Yori and the moral implications of their relationship. Their dynamic is further complicated by the presence of other characters, including classmates and friends who unknowingly influence their decisions. The series portrays their journey as they confront societal taboos, familial expectations, and their own desires, creating a tense and emotionally charged atmosphere.

The plot unfolds through a series of intimate and dramatic moments, highlighting the siblings' attempts to balance their secret relationship with their public lives. The story does not shy away from the complexities of their situation, presenting their love as both tender and fraught with challenges. Themes of secrecy, sacrifice, and the boundaries of love are central to the narrative, making it a thought-provoking exploration of unconventional relationships. The anime maintains a focus on the emotional depth of its characters, offering a nuanced portrayal of their struggles and the consequences of their choices.