Help me find this Yaoi?

So the MC works as a mechanical engineer (idk if I'm correct) and one day the ML ask him to fix his car and the MC fix it but decided to loose a bit of his engine so he can come again. The ML ask the MC if he was a regular would he get a special service and then start kissing and MC found a gun in the car and knows the ML is a mafia. If I remember the Main lead has a blond hair, his hair is shaved like an army hair (typically I guess)