His photo.

A few days ago, my boyfriend's aunt asked me, "Why don't you put his photo as your phone's wallpaper?"

I couldn't come up with an answer then.

But today, I have an answer: I don't need the whole world to know he's mine. As long as I know he's mine, and that he has my heart like how I have his, that's what matters to me. I don't need to show the whole world that he's my guy when I'm using my phone. I don't need people to ask me, 'Who's this? Your boyfriend?' when they see my phone's wallpaper. I don't need to show him off to the world.