The densest subgraph problem is an important problem with both theoretical and practical significance. We consider a variant of the problem, the directed densest subgraph problem, under the partially dynamic setting of edge insertions only. We give a algorithm maintaining a (1-ε)-approximate directed densest subgraph in O(log3n/ε6) amortized time per edge insertion, based on earlier work by Chekuri and Quanrud. This result partially improves on an earlier result by Sawlani and Wang, which guarantees O(log5n/ε7) worst case time for edge insertions and deletions.