a wild relative of the soursop?

this wild fruit, as shown above, has a similarity to the regular soursop:   skin texture, smell and color.  Both leaves of the regular soursop and the wild version smells the same, only the wild one is a bit slimmer. (The light green oblong beside the fruit is the bud.) The size however, is just about 1/20 of the popular and otherwise the regular sousop below:

 

The flesh is also white and fibrous.  But is it edible? Anyone knows what this wild fruit's name is? We discovered its existence recently when we went to an old friend's small coffee plantation.

                                   It was long way up, but it was worth it.