Solving Queen Ophelia's Mysterious Death

On the verge of death, Queen Ophelia wished, "I want to know who killed me." Then, in accordance with an "ancient promise" given only to the owner of the crown, the Fairy King Leah brought her back to life for just ten days! "I died once, so this time, I will do whatever I want." Ophelia's husband, who tried to use her to seize power... Her brother, who is unreliable and tends to be swayed by those around him... A knight of the royal guard who has fallen in love with her... The list of possible culprits is endless. Who killed the queen?! A royal mystery begins in the palace with a strong slap that will clear the queen's name before her death! (Source: Kadokawa, translated)