I Was the Tutor of the Obsessive Grand Duke

I became the tutor of Rubeteo, a young boy and the illegitimate son of the Emperor. Yurkia was asked to be his tutor only until he came of age, as he would be the future Crown Prince. Timid by nature, he wanted to refuse, but by the Emperor's command, he had no choice but to go north, where Rubeteo was. The boy he first encountered didn't speak and showed no emotion. But perhaps thanks to Yurkia's touch, as warm as sunlight, Rubeteo was unusually fond of Yurkia. Time passed, and the day of Rubeteo's coming-of-age ceremony, which was the promised day, arrived. Thinking it was finally over, Yurkia tried to leave the Empire and return to his own life, but- "Yuri, are you leaving me behind?" ...