Boku wa Kimi dake o Mitsumeru ~I Gaze at Only You~

The protagonist Sahara Takumi was feared as the leader of the juvenile gangster group “Sabre-tooth Tiger”. Some people in the underworld even called him devil’s incarnate, and so far the police has been unable to capture him.

Then suddenly two of his best friends are killed by an assassin employed by the mafia. The event marked the downfall of Sabre-tooth Tiger and Takumi made sure he stayed out of public attention. Despite even all that he receives a request to be the bodyguard for a mysterious diva named Towa. Seeking revenge for his comrades and a way to rise up from this nightmare, the protagonist accepts the job and stands up to act as Towa’s shield.

[From Otaku Lair]

This game was initially released as doujin game by RainDog, Inre's doujin group name before went as commercial developer.