"Unfaithful" is a song from Rihanna and was featured in the Season Twenty-One episode "Doubling Down".
Background
The song plays during a montage as Heidi looks through a photobook of her memories with Cartman. During the montage, she looks at Kyle down the corridor. She leaves Cartman crying on a bench. Kyle opens a letter, presumably from her. Mr Garrison is seen speaking to a foreign leader. Finally, Heidi and Kyle are seen on the swings.
Lyrics
Story of my life
Searching for the right
But it keeps avoiding me
Sorrow in my soul
Cause it seems that wrong
Really loves my company
He's more than a man
And this is more than love
The reason that the sky is blue
The clouds are rolling in
Because I'm gone again
And to him I just can't be true
And I know that he knows I'm unfaithful
And it kills him inside
To know that I am happy with some other guy
I can see him dying
I don't wanna do this anymore
I don't wanna be the reason why
Every time I walk out the door
I see him die a little more inside
I don't wanna hurt him anymore
I don't wanna take away his life
I don't wanna be
A murderer
I feel it in the air
As I'm doing my hair
Preparing for another date
A kiss upon my cheek
As he reluctantly
Asks if I'm gonna be out late
I say I won't be long
Just hanging with the girls
A lie I didn't have to tell
Because we both know
Where I'm about to go
And we know it very well
Cause I know that he knows I'm unfaithful
And it kills him inside
To know that I am happy with some other guy
I can see him dying
I don't wanna do this anymore
I don't wanna be the reason why
Every time I walk out the door
I see him die a little more inside
I don't wanna hurt him anymore
I don't wanna take away his life
I don't wanna be
A murderer
Our love, his trust
I might as well take a gun and put it to his head
Get it over with
I don't wanna do this
Anymore
Uh
Anymore (anymore)
I don't wanna do this anymore
I don't wanna be the reason why
And every time I walk out the door
I see him die a little more inside
And I don't wanna hurt him anymore
I don't wanna take away his life
I don't wanna be
A murderer (a murderer)
No no no no
Yeah yeah yeah yeah