The Apothecary Diaries, Volume 11 (by Natsu Hyuuga)

After breaking a “curse” on the imperial heirs, a palace servant with training in herbal medicine is promoted up the ranks to food taster...and right into the thick of palace intrigue in this lushly illustrated historical mystery series!

Summoned to attend the Emperor on an evening jaunt to an ancient shrine that functions as a rite of passage for the rulers of the land, Maomao makes quick work of the puzzle inside, acquitting herself with aplomb. Having learned more about the Imperial bloodline than a commoner has any right to know, Maomao returns to her post at the Jade Palace. But her aim to stay out of the business of her betters is foiled once again when the Empress Dowager comes calling! The mother of His Imperial Majesty seeks Maomao's aid in investigating yet another curse, one she fears she herself may have cast upon the infamous late Emperor...