The Wikipedia article on Mitsubishi A6M Zero fighter cites an article from Life magazine published on Nov 4, 1942:
The Zero's fuselage and wings were constructed in one piece, unlike the American method that built them separately and joined the two parts together. The Japanese method was much slower, but resulted in a very strong structure and improved close maneuverability.— Wikipedia
This design is harder to implement but it allows for higher strengths for the same weight or lighter weight for the same required strength.
Is there a name for such fuselage design?