From Renta!:

Exhausted from the office, Shuichi Takayama heads home for a good night's sleep. Unfortunately, his younger brother Toji has other ideas, stopping by unexpectedly in the middle of the night. Shuichi asks his brother to leave, but Toji's not alone. He's brought Hayato Asakura, a runaway he just met at the convenience store! Hayato decides to stay at the businessman's place indefinitely. No matter how hard Shuichi tries, he fails to convince the high schooler to leave. He later realizes he can't kick Hayato out after learning why he left home to begin with... Despite Hayato being somewhat mysterious, unusual and controlling - and 15 years younger - Shuichi decides to take him in! What will become of this 30-something workaholic and the mischievous young man who's wrapped around his little finger!?