Agasawa Tea, also known by the name Kocha Agasawa, is a Japanese manga artist and the original creator behind the anime series The Ramparts of Ice and You and I Are Polar Opposites. The creator began their career in manga while working as an ordinary office worker, initially creating work in their spare time. The debut work, The Ramparts of Ice, was a successful web manga that won an award. However, facing the dual pressures of a full-time job and the demands of a weekly serialization, the creator considered giving up on manga entirely. Lacking the confidence to become a full-time artist, a plan was devised to create another short story. This new work was intended to test their true abilities as a creator and also help attract readers to their first series. This short story ultimately became the basis for You and I Are Polar Opposites.

The first major work, The Ramparts of Ice (Koori no Jyōheki), is a web manga that was initially published as a digital webtoon. It was serialized on Line Corporation's digital Line Manga service from January 10, 2020, to April 28, 2022. The series was later collected into fourteen tankōbon volumes published by Shueisha under the Jump Comics imprint. The story follows Koyuki Hikawa, a high school freshman known as the queen for her cold and distant nature who avoids socializing, as she navigates unexpected friendships. An anime television adaptation produced by Studio Kai is scheduled to premiere on April 2, 2026.

The subsequent work, You and I Are Polar Opposites (Seihantai na Kimi to Boku), began as a one-shot short story created during the creator's period of uncertainty. The positive response to this test led to full serialization, which ran from May 2, 2022, to November 25, 2024. The series was published in eight volumes and became a significant commercial and critical success, with over 1.45 million copies sold. The story centers on Miyu Suzuki, a cheerful and outgoing high school girl who confesses her feelings to Yusuke Tani, a quiet and stoic classmate who is her complete opposite. The manga won second place in the Web category of the Next Manga Award in 2022, placed third in the Manga Taishō in 2023, and placed seventh in the Manga Taishō in 2024. A television anime adaptation began airing in January 2026.

A distinct artistic identity is present across these works. The creator is known for breaking from traditional slow-paced romance conventions, as seen when the female protagonist confesses her feelings in the very first chapter of You and I Are Polar Opposites. To avoid emotional disconnection from this fast pace, comedic elements are skillfully incorporated. The characters are noted for their realism; they are ordinary people who fear getting hurt but deeply yearn to connect with others, rather than idealized heroes or figures in earth-shattering dramas. The art style is described as refreshing and the storytelling as lighthearted. The creator's experience with webtoon serialization led to an understanding of modern reading habits, with a conscious technique of placing a suspense point every four to five pages in the manga. In 2026, an illustration was released to celebrate the anime adaptations of both series airing in the same year, symbolizing a passing of the torch from You and I Are Polar Opposites to The Ramparts of Ice.