Maarui Kanojo to Zannen na Kareshi, known in English as Chubby Girlfriend & Pity Boyfriend, is a romantic comedy centered on Mariko Hosoi, a full-figured nurse who loves to eat but has no romantic experience and assumes she will be single forever. Her life takes an unexpected turn when she is invited to a group date and meets Nagi Kirigaya, a handsome man who surprises her by showing genuine interest and asking her out on a solo date. The story follows the awkward yet endearing romance that develops between an insecure woman and the unexpectedly sincere man who sees past her doubts.

Mariko Hosoi is a kind-hearted nurse whose lack of confidence in her appearance has led her to accept a life devoid of romance. Nagi Kirigaya is the charming and good-looking man whose straightforward pursuit of Mariko is the central catalyst of the plot. While Nagi appears perfect on the surface, the title hints at his own flaws or a "pitiful" aspect of his personality that becomes apparent as their relationship deepens.

The setting is contemporary Japan, balancing Mariko’s workplace as a nurse with everyday locations like restaurants and date spots where their romance unfolds. Originating as a web manga by Izumi Hayama with illustrations by Yachiyo Okamura, the series gained over 80 million views in Japan before receiving a short-form television anime adaptation. The narrative primarily follows the main couple's journey from an unexpected meeting to dating, focusing on Mariko’s gradual growth in self-esteem as she navigates her first real relationship. Nagi’s consistent pursuit of her forces Mariko to confront her insecurities, leading to romantic milestones and comedic situations born from her inexperience and surprise at being wanted. Their relationship development is the core arc, centered on how two people overcome their respective flaws and insecurities to build a genuine connection.