My Lover's Secret(愛してたって、秘密はある。)

Lead character Rei Okumori was in his last year of middle school when he killed his father to protect his mother from domestic violence. Rei and his mother Shoko buried the corpse in the yard, dumped the father's favorite car in the ocean, and staged everything to look like a missing person case. Just like that, Rei's crime became a "secret" between only him and his mother. He decides he doesn't need any friends or a girlfriend and lives under the radar without forming deep relationships with anyone. Rei works tirelessly to become a lawyer--a dream that is the only meaning he finds in life. Shoko blames herself for being the reason her son has to bear a heavy burden for life and wishes from the bottom of her heart that he will be happy. Eight years after the murder, Rei meets Sawa Tachibana, an innocent girl who attends the same law school and dreams of becoming a prosecutor. Sawa is a flash of light that enters the darkness in which Rei has walked all these years. They fall in love and Rei obliges his mother and girlfriend's wish that they get married. Just when Rei and Sawa decide to get married, someone who knows the "secret" begins to send eerie messages.