Satsuriku no Tenshi EP15 - A Vow Cannot Be Stolen.

Ray and Zack flee up the stairs as the facility begins to burn and collapse, but their way is blocked by steel bars. Zack briefly has a panic attack due to his fear of fire, but he manages to regain his senses upon seeing Ray struggling to break the bars. Overcoming his fear, Zack manages to break through the bars and all other obstacles, though he breaks his scythe in the process. They finally reach the top floor, where Ray asks Zack if he truly wants to kill her, and she wouldn't fault him if he changed his mind. Zack reaffirms the promise he made when Danny arrives and shoots Ray in the back. He reveals he was the one who activated the self-destruct sequence and holds Zack at gunpoint to watch Ray die, so he will have to live with the knowledge he couldn't fulfill his promise. Ray assures Zack that she doesn't care if their vow is fulfilled or not, only that the vow was made in the first place, and she will carry the burden of their vow so Zack doesn't need to think of himself as a liar. Jealous of Ray's affection for Zack, Danny shoots Ray again and prepares to kill Zack when Gray disables him with a crossbow. Grey orders Zack to leave through the exit, assuring him there is still a chance to save Ray. Zack picks up Ray's body and heads for the door with Danny still pointing his gun at his back.