Amatsuki, the manga series written and illustrated by Ai Morinaga, has been on hiatus since September 2021 due to the author's health issues. As a result, chapter 40 has not been released yet. As of now, there is no update on when the manga will resume publication.
Please note that this information is up-to-date as of February 2023. Since the manga's status may change in the future, I recommend checking the official sources for the most current information.