From Lezhin:
During the period of Japanese colonial rule, a young Korean boy, Yonghyun, is invited every summer to a royal residence in the mountains behind his village. The residence of one Count Tachibana. The peculiar Tachibana Sho is a complete mystery, as it seems he’s never left his mansion, not even once. But over the summers, Tachibana Sho and Yonghyun have made a strange but solid bond with each other. Now Yonghyun is devising a plan to help Sho escape his mansion but it won't be easy. Adults with their meddlesome ulterior motives and the giant mansion itself all present challenges to their idea. How will the two boys break free and what will they learn about each other...?