Serika is an office worker in her twenties who ends up living with her younger cousin Taichi, a university student six years her junior, after he passes his entrance exams and needs a place to stay until he finds his own apartment. Serika remembers Taichi as a sweet, gentle-natured boy with delicate features, but the years apart have transformed him into a confident and possessive young man. Almost immediately he begins pursuing her with a direct, domineering intensity that catches her completely off guard, hugging her and kissing her without warning and pushing her self-control to its limits.

Despite the taboo of their familial relationship, Serika and Taichi enter a secret romantic and physical relationship. The story follows the development of their bond as they navigate the challenges of keeping their love hidden from family and colleagues. Taichi is obsessive, protective, and relentless in his desire for Serika, often acting with a jealous and sadistic edge that contrasts sharply with his angelic appearance. Serika, for her part, struggles between her lingering sense of propriety and the powerful attraction she feels for the man Taichi has become.

As the series progresses, the couple deepens their commitment. Taichi proposes and the two become secretly engaged, though they continue to face obstacles. Serika’s company colleague and former university senior Seo develops feelings for her and refuses to give up even knowing she is taken, creating a tense love triangle. A major narrative arc involves Serika’s mother discovering the relationship, leading to a period of coldness and family strain. Taichi’s own father eventually learns the truth after walking in on them during a trip, forcing the couple to confront their families directly.

Another pivotal arc sees Taichi suffer a serious accident shortly after the couple begins cohabiting in a new apartment. Doctors warn that he may be left with permanent damage to his leg. The injury tests both characters deeply: Taichi struggles with fear and uncertainty about his future, while Serika endures the loneliness of their separation during his hospital stay. Their time apart ultimately leads to a raw, honest conversation and a rekindling of their physical intimacy within the confines of the hospital room, reaffirming their bond.

Throughout the many chapters, the manga focuses almost exclusively on the central couple, with each new volume introducing fresh complications—rival characters, family opposition, career pressures, and health crises—that serve to reinforce rather than break their connection. The art style emphasizes expressive faces and sensual, charged atmospheres. The series remains ongoing as of its twenty-second collected volume, published by Shogakukan in their Flower Comics Alpha imprint under the serialization label Mobile Flower, written and illustrated by Uta Nashizuki.