Basically, Aoi was dating Reita but cheated on him with Uruha. Finally Aoi decided to stop playing around and leave him for his fellow guitarist. To understand it properly read the lyrics:

[REITA]
I'm gonna make it bend and break.
Say a prayer, but let the good times roll,
In case god doesn't show.

Let the good times roll.
Let the good times roll.

[REITA]
And I want these words to make things right,
But it's the wrongs that make the words come to life.
"Who does he think he is?"

[REITA to URUHA]
If that's the worst you got,
Better put your fingers back to the keys.

[AOI to URUHA]
One night and one more time.
[AOI to REITA]
Thanks for the memories,
Even though they weren't so great.
"He tastes like you only sweeter."

[AOI to URUHA]
One night, yeah, and one more time.
Thanks for the memories.
Thanks for the memories.
[AOI to REITA]
"See, he tastes like you only sweeter."

Ohhhhhh.

[AOI]
Been looking forward to the future,
But my eyesight is going bad.
And this crystal ball,
Is always cloudy,
Except for when you look into the past.
One night stand.
One night stand.

(CHORUS)

[URUHA]
They say I only think in the form of crunching numbers.
In hotel rooms,
Collecting page six lovers.
Get me out of my mind.
Get you out of those clothes.
[Uruha to Aoi]
I'm a liner away,
From getting you into the mood.
Woooah.

(CHORUS)