I actually got shivers when reading this, and the end was really unexpected. I really liked the way you showed the friendship between them, particularly the sentence beginning 'Our hearts plugged...'. Very chilling but a good read (:

Heh! Heh! Clearly the narrator is quite childlike and may be described as a bit simple. Entertaining and I enjoyed reading it to the end.

As for suggestions to improve it...I'm at a loss really. I think the story unfolded well and it had the necessary naive telling of the tale by the narrator. The only thing I would say is that the story was so well told that the last phrase "Together is death..." wasn't necessarily needed.

I really like your writing. I really do.