Boy's Abyss, Vol. 6 (manga)

Author Kosaku Esemori met Reiji’s mother when he first arrived in their miserable backwater as a teenager, which begs the question: who is Reiji and his abusive older brother’s real father? Then, it turns out Reiji and Nagi aren’t the only ones in town with suicidal ideation. Is it true that a double suicide unites two souls as one? (Hint: The answer is no.)