The Apothecary Diaries, Volume 13 (by Natsu Hyuuga)

Maomao has accompanied Jinshi on a hunting trip in which Jinshi is keeping his true identity a secret. But then they were suddenly shot by flintlocks and managed to get away by hiding in a cave where Maomao learns one of the many secrets that Jinshi has been keeping. Now she has to work with Lihaku to identify their would-be assassins. While she’s able to work out their motive, could it be that there’s much more to this incident than she realizes? Once this case is closed, Maomao is once again called upon to solve a mystery in the inner court!