In the Heart of Kunoichi Tsubaki (Japanese: くノ一ツバキの胸の内, Hepburn: Kunoichi Tsubaki no Mune no Uchi) is a Japanese manga series written and illustrated by Sōichirō Yamamoto. It has been serialized in Shogakukan's shōnen manga magazine Monthly Shōnen Sunday since January 2018. An anime television series adaptation by CloverWorks aired from April to July 2022.