"Hatsujō DNA" is a manga series that explores themes of adolescence, identity, and the complexities of human relationships through a blend of drama and psychological elements. The narrative centers around a high school student named Riku, who becomes entangled in a peculiar phenomenon involving a mysterious DNA-altering substance. This substance, which begins circulating among the students, triggers heightened emotional and physical responses, particularly amplifying their sexual desires and instincts. As the effects spread, the school environment becomes increasingly chaotic, with students struggling to navigate their newfound impulses and the societal pressures surrounding them.

Riku, initially a reserved and introverted individual, finds himself at the center of the unfolding events. His interactions with classmates, including the confident and assertive Aoi and the enigmatic transfer student Yuna, reveal deeper layers of his personality and past. The story delves into the psychological impact of the DNA phenomenon on Riku and his peers, examining how it forces them to confront their insecurities, desires, and the boundaries of their relationships. As the situation escalates, the students must grapple with the ethical and moral dilemmas posed by the substance, as well as the consequences of their actions.

The plot intertwines personal struggles with broader societal commentary, addressing themes such as peer pressure, the search for identity, and the impact of external influences on human behavior. The characters' development is closely tied to their reactions to the DNA phenomenon, with each individual's journey reflecting different facets of adolescence and self-discovery. The series maintains a focus on the emotional and psychological growth of its characters, using the DNA-altering substance as a catalyst to explore their inner conflicts and evolving relationships. Through its narrative, "Hatsujō DNA" presents a thought-provoking examination of human nature and the challenges of navigating the transition to adulthood.