Do you mean subs on the MV or just a translation of the lyrics?
Cause if it's just the translation, Tenshi no Hane has already got you covered there, friend.
http://tenshiscave.tumblr.com/post/1...ion-dear-diary
But if you're looking for subs on the video
I've never seen someone do it for a namie video. I would, but I don't know how/don't have the right programs