"At 30, I Realized I Had No Gender" explores the life of Itsuki Ichihara, a 30-year-old office worker who begins to question their identity after a lifetime of conforming to societal expectations. The narrative delves into Itsuki's journey of self-discovery as they come to terms with their non-binary identity, a realization that challenges their understanding of gender and self. The story is set in a contemporary Japanese workplace, where societal norms and pressures often dictate rigid gender roles.

Itsuki's journey begins with a growing sense of discomfort and detachment from the gendered expectations placed upon them. This discomfort is exacerbated by interactions with colleagues and societal norms, leading to a pivotal moment of introspection. Through conversations with friends, family, and a supportive therapist, Itsuki begins to explore the concept of gender beyond the binary framework. The manga thoughtfully portrays their internal struggles, moments of doubt, and eventual acceptance of their identity.

Key characters include Itsuki's childhood friend, Yui, who provides emotional support and a safe space for Itsuki to express their feelings. Yui's role is instrumental in helping Itsuki navigate their evolving identity. Another significant character is Itsuki's therapist, Dr. Saito, who offers professional guidance and helps Itsuki articulate their thoughts and emotions. The workplace environment also plays a crucial role, with colleagues representing a spectrum of reactions to Itsuki's journey, ranging from confusion and skepticism to understanding and acceptance.

The plot progresses through Itsuki's daily life, blending moments of introspection with external challenges. The manga addresses themes of self-acceptance, societal expectations, and the complexities of gender identity. It highlights the importance of support systems and the impact of societal norms on individual identity. The narrative is grounded in realism, portraying Itsuki's experiences with sensitivity and depth, making it a poignant exploration of gender identity in a contemporary setting.