Hangman

Did he even steal from his older brother, who grew up in the same boat? Han Ji-Chan was different from birth, and it felt natural to be superior to others. Unchanging routines breed boredom. As usual, Ji-Chan was cleaning up after his brother's missteps and heading home when he saw a strange man, Su-Hyuk. And he was having sex with his older brother.

(Source: Lezhin, translated)