A Star Brighter Than the Sun is a romance anime television series that aired from October to December 2025, produced by Studio KAI and based on the manga by Kazune Kawahara. The story centers on Sae Iwata, a tall and physically strong girl who has always felt less dainty than her peers, and her childhood friend Kouki Kamishiro, who was once a delicate and fragile boy she felt the need to protect. As they progressed through middle school, Kouki experienced a significant growth spurt and became taller, more confident, and popular, leading the two childhood friends to drift apart. Toward the end of their third year of middle school, Sae and Kouki reconnect, and her dormant romantic feelings for him resurface. The situation becomes more complicated when they discover they have been placed in the same class upon entering high school.

The series is set in Hokkaido, following Sae and Kouki through their daily lives, school events, and the evolving dynamics of their friend group. Sae Iwata is the protagonist, a kind-hearted but insecure girl who struggles with her feelings and her perception of not being feminine or cute enough for Kouki. Kouki Kamishiro is the male lead, a seemingly perfect and sunny-natured boy who remains unaware of the depth of Sae's feelings, even as he holds a secret crush of his own. The supporting cast includes their classmates: the gentle Hisui Onodera, the serious Mio Kagawa, the friendly Yota Ayukawa, and the blunt Yushin Izawa. A notable supporting character is Subaru Kamishiro, Kouki's cousin, whose presence introduces moments of narrative tension.

The first season unfolds over twelve episodes, adapting the manga's early story arcs. The narrative follows Sae as she attempts to suppress her deepening feelings for Kouki while navigating the unfamiliar territory of high school. A key arc involves a school trip where Kouki confesses to Sae that he has feelings for someone he describes as a star brighter than the sun, a comment that deepens her internal conflict as she assumes he could not be talking about her. Throughout the season, Sae and Kouki are brought together by various school events, including a jump rope tournament, a class play, and a movie date, all of which serve to strengthen their bond while misunderstandings persist. The final arc of the season focuses on the school festival, where Sae decides to confess her feelings. After a series of events involving Kouki's cousin Subaru, Sae overhears that Kouki plans to confess to his own crush. Believing she has no chance, she impulsively blurts out her feelings to him and runs away. The season concludes with Kouki finding her in a gym storage room, leading to a resolution of their mutual feelings. A second season has been announced.