Disclaimer: Sadly, I do not own Naruto, and I never will. If I did, all my ships would have been canon.
Dear brat, no, dear Deidara,
I'm sorry for dying, something I never expected would happen, but just in case, I wrote this letter, because I want to die without regrets. After all, I am, no I was an incomplete puppet, capable of human emotions. Emotions I didn't think I had, until I met you. You, with your loud, annoying and bright attitude, never failed to make me feel less like a puppet and more like a human being, something I loathed being. But somehow, I couldn't hate you for it, nor for the insults you threw my way when we talked about art. I found joy in our arguments, in seeing your eyes light up when talking about your favourite thing, your art. And somewhere between those arguments I found myself for some reason wishing that you would talk about me with the same light in your eyes. Over time, this strange, warm feeling grew in my chest whenever I was around you, and it wasn't until later, after a lot of research, that I came to know this feeling by the name everyone called it, 'love'. I had never loved someone before, my parents only a distant memory, I had once had strong feelings for my grandma, I remember that, but I wouldn't dare call it 'love', because it is nothing compared to this. I liked this feeling of 'love', it made me feel all comfortable and warm, and I felt like I could conquer everything and everyone whenever you called me "Danna". That's when I realized that maybe being human wasn't so bad after all. I opened up to these emotions that I felt, learning to recognize them again, as they were something I had long forgotten. I knew the feeling of 'worry' whenever you were fighting a strong enemy, 'fear' when you got hurt, 'pain' when I learned about your ultimate jutsu, 'pride' whenever you beat an enemy and above all 'love' at all times. And what I hate the most about dying is the fact that I will never be able to see your passion again, your adorable 'hm' and that o so amazing light in your eyes, those eyes that gave me hope. I'm so sorry for leaving you, Deidara, please forgive me.
Why did you have to die, Danna? You said you were eternal, that you would continue to exist forever. Why did you lie? And why did you never tell me about your feelings, because I love you too, Sasori no danna. I will always continue to love you, and I will never let anyone take you away from me. They gave me a new partner, and they told me he was your replacement, and I got mad and tried to blow him up, because I hoped that maybe you would come back and criticize my art. You didn't… why, why didn't you?!
Please fight on for me, stay alive, fulfill your goals, please, I don't want you to die, too. Don't let anyone extinguish your light, don't let anyone bring you down. I wish I could come back to you, see your face again, but I can't. I'm gone, Deidara, and I'm not coming back, please accept that and move on. Do not grieve for someone who is neither puppet nor human, a failure as both.
You are not a failure, Sasori! I have always looked up to you as my master, and in the end, you won the argument: I now understand how fleeting things aren't always beautiful, oh how I wish you were eternal, yes, I can finally agree with you, eternal beauty is, indeed, art. But so is fleeting beauty, and I will now die in the same sudden moment as you did. Especially for you, I perfected my final and ultimate art, so watch me as I show you the truest art of all, and maybe then we'll finally be together again.
"Art is eternal!"
"Art is an explosion, hm!"
"You don't understand true art!"
"Neither do you, Sasori no Danna!"
"Katsu!"
In the end, I became just like your art, a fleeting moment, a sudden end, a finished story. But I don't think that I mind, because it makes me a part of you… your work of art, something you so carefully created, only to disappear in a single moment. Maybe now, we can finally agree for once. Our deaths are our final artwork, a collaborative piece, and a final statement. Art is eternal beauty, coming to an end in a single, fleeting moment.