Osamu Kajisa (加治佐 修, Kajisa Osamu) born December 30, 1973, is a Japanese mangaka and former assistant to Kishimoto Masashi. Following his work on Naruto, he went on to moderate success and is best known for the manga series Tattoo Hearts, which was serialized in Weekly Shonen Jump in 2003.

Also goes by the pen name Kajio(カジオ). Which is a combination of his surname, Kajisa, and the first letter of his given name Osamu, hence Kaji-o. Used for DD Fist of the North Star.