Unmyeongui Yuillon

At an orphanage, a child appears before Lee Seo-Hu, who had rejected everyone but himself, and clings to him persistently. Before he knows it, Seo-Hu has lost his heart to the child, names him "Yu-Il," and begins to obsess over him, binding him to his life. However, the world keeps trying to snatch Yu-Il away from Seo-Hu in various forms. Although Seo-Hu never let Yu-Il go despite numerous crises, they drift apart once again when Yu-Il manifests as an All-rounder Guide. Seo-Hu begins to take action once more to make Yu-Il his own...

(Source: Bomtoon, translated)