"Itsudatte My Santa" is a romantic comedy manga series that blends elements of fantasy and holiday themes. The story centers around Santa May, a young girl who claims to be Santa Claus and appears in the life of a high school student named Minoru Utsugi. May arrives unexpectedly on Christmas Eve, declaring that she has come to grant Minoru a wish. Initially skeptical, Minoru dismisses her claims, but her persistence and the inexplicable events surrounding her presence gradually make him question her true identity.

Minoru is a pragmatic and somewhat cynical teenager who has lost faith in the magic of Christmas due to past disappointments. May, on the other hand, is cheerful, determined, and deeply committed to her role as Santa, though her methods are often unconventional and comically flawed. As the story progresses, it becomes clear that May’s mission is not just about granting wishes but also about rekindling Minoru’s belief in hope and joy.

The narrative unfolds over a series of episodic adventures, with May attempting to fulfill Minoru’s wishes while navigating the challenges of her own limited powers and the skepticism of those around her. Along the way, the two form a close bond, and Minoru begins to see the value in May’s optimism and kindness. The story also introduces other characters, such as Minoru’s classmates and family members, who add depth to the interactions and provide additional comedic and emotional moments.

A recurring theme is the tension between May’s fantastical claims and the grounded reality of Minoru’s world. This dynamic drives much of the humor and conflict, as May’s attempts to prove her identity often lead to chaotic and heartwarming situations. The series balances lighthearted comedy with moments of genuine emotion, particularly as Minoru’s backstory and the reasons for his disillusionment are revealed.

As the story progresses, the focus shifts from May’s initial mission to the growing connection between her and Minoru. Their relationship evolves from one of skepticism and frustration to mutual understanding and affection. The series concludes with a resolution that ties together the themes of belief, hope, and the transformative power of kindness, leaving the characters—and the readers—with a sense of closure and warmth.