The first anime adaptation under the title One: Kagayaku Kisetsu e is produced by he Japanese animation studio KSS, written and directed by Yōsei Morino, and features character design by Jun Satō who based the designs on Itaru Hinoue's original concept. Four episodes were produced which were released separately as OVAs on Region 2 DVDs between August 10, 2001 and May 24, 2002 by KSS. The series was re-released as a one-disc DVD box set on February 29, 2008 by JSDSS.