((Your boyfriend is secretly a spy, and he has been given the mission to survey a rich girl who was the daughter of the first minister, so he has to fake the fact for being his boyfriend... Even if you're his real girlfriend))

So for you recently discovered that your boyfriend Alex was cheating on you

A day, Alex was coming back from his 'work', but he was having a mark of lipstick on his neck..

"Hello love, how has been your day?"

He asked like if he did nothing