His mother got pregnant at a young age and decided to give birth to him. She devoted her life and youth as a single mother to raise her son.

Feeling guilty over her inability to give her only family a normal lifestyle, she even offered her own body to her sexually awakened son; Nevertheless, he grew up to be a fine young man (with a raging mother complex, however). Wanting to ease the burden on his mother sooner, he puts his heart into looking for a job; and once their lifestyle stabilizes, he plans to "give back to her" in order to grant her that desire that she's always had.

(Source: DMM)