No one, but him.

The young Arwen looked confused. Blinking her eyes at the young boy, she asked, "Promise? What promise, Ide?" 

The young guy stared at her for a moment before finally saying, "Promise to be my girlfriend now and wife later." 

"Girlfriend? Wife? What does that have to do with taking a picture?" The little girl titled her head, her face filled with innocent confusion. 

But to the boy, this seemed to be a serious matter. Without creating further suspense, he explained, "A picture together makes a marriage certificate complete. Do you think taking a picture is something simple?" 

Seeing the girl blink at him in deep thought, he shook his head and continued, "'It's not. That's why if I take a picture with a girl, she has to be my girlfriend and, in the future, my wife. That way, she won't feel jealous of anyone else later." 

The girl paused at his words, her small face scrunched in thought, as if she was truly considering his reasoning.