Tekzhu and Zhenya

Taekju is an ordinary guy, the son of a physician. From childhood, he studied herbs and medicines, and tested the effects of poisons on himself. He lived in poverty in a dangerous neighborhood.

Eugenius (Zhenya) is the youngest son of the former emperor and a possible heir to the throne. He has white hair and blue eyes. He is an excellent swordsman. His loyal advisor, Caesar, is always at his side.

The Emperor is the eldest son of the previous Emperor. Calm, wise, and fair.

Irina is an artist and poetess of the courtyard, a good friend of Taekju.

Vanya and Ivan are guards. Ivan is calm and reasonable, Vanya is energetic and constantly seeking adventure.

Concubines: Idia - kind and friendly;
Paradise is calm and sensitive;
Darina is the youngest, she tries to appear older;
Mitsuya is mysterious and cold.

Egor is a blacksmith, Artur is his assistant.

Plot

While gathering herbs, Taekju is kidnapped and sold to the palace. He initially works as a simple servant, then meets Irina, and they become friends.
Soon, Idia gives birth to a daughter, and Raya to a son, an heir. But both children become gravely ill. The heir dies a week later, and Raya, unable to bear the grief, falls gravely ill herself. Idia's daughter also finds herself on the brink of death.
Taekju begins an investigation and discovers that the cause is the powder used by the palace women. It contains a poisonous mineral, especially dangerous for children.
Not wanting to reveal his identity, he writes two words on a scrap of cloth at night: "Powder. Poison." and leaves it on the palace steps. Zhenya finds the note and begins searching for the person who wrote it, as only the emperor, himself, Caesar, and the concubines are allowed to read and write in the palace.