Surpassing 600,000 copies in total! Yuko Yuzuki's popular 'Sadato Sakata' series releases its first full-length novel in 16 years, 'Testimony of the Vow,' on March 26.

KADOKAWA Corporation (Headquarters: Chiyoda-ku, Tokyo) released Yuko Yuzuki's new full-length novel, "Testimony of the Vow," on Thursday, March 26, 2026. This work is the fifth installment in the "Sadato Sakata" series, which has surpassed 600,000 copies in total. It marks the first full-length lawyer-focused novel in the series in 16 years, since the first book, "The Last Witness."

The story moves between Kagawa and Tokyo. The Kagawa segment highlights the passionate dedication of craftsmen working with the traditional "Baneiseki" stone, while the Tokyo segment features intense courtroom battles and tactical maneuvering between the prosecution and Sakata. It is a highly recommended read for both long-time fans of the series and newcomers alike. Please stay tuned!

"Sadato Sakata" Series Special Site

◆ Highlights of this work

★ Set in Kagawa Prefecture! The passion and conflict of traditional stone craftsmen

The story alternates between the Kagawa segment, told from the perspective of Takeru Ohashi, a stone craftsman in Baneicho, Kagawa—the production site of the high-quality "Baneiseki" stone—and the Tokyo segment, told from the perspective of lawyer Sadato Sakata. When these two seemingly unrelated stories intersect, the determination of a certain woman comes to light.

The highlight of the Kagawa segment is the passion and conflict of the craftsmen dedicated to the beautiful and durable "Baneiseki" stone.

Should they preserve traditional methods, or move toward mass production for the future?

★ A legal suspense novel where Sakata's courtroom arguments shine and deep friendship warms the heart!

Sakata decides to believe in his old friend Kubo, who maintains his innocence. In a trial where the odds seem stacked against him due to unfavorable evidence, Sakata finds a chance for a reversal and employs a "daring strategy."