When the PS Vita was released, Sony implemented a new DRM system, known as "PS Vita DRM" or "NPDRM." This system required games to be authenticated online, which meant that users had to have an active internet connection to play their games, even in single-player mode.
The version you're mentioning, specifically, is a USA release for the PS Vita, with the interesting addition of "NoNpDrm" in the title.
However, I must emphasize that the discussion of game piracy, emulation, and homebrew usage is a separate topic. Ninja Gaiden Sigma Plus PS VITA -USA- -NoNpDrm-
The USA release of Ninja Gaiden Sigma Plus for the PS Vita, specifically with the "NoNpDrm" label, indicated that the game had been patched to remove the DRM protection. This meant that players could enjoy the game without any online requirements, making it a more appealing option for those who preferred to play offline.
However, some developers and publishers pushed back against this requirement, and Tecmo Koei was one of them. They decided to create a special "NoNpDrm" version of Ninja Gaiden Sigma Plus for the PS Vita, which would allow players to play the game without the need for an online connection. When the PS Vita was released, Sony implemented
The NoNpDrm patch, in particular, ensured that players could enjoy the game without restrictions, showcasing a somewhat unusual alliance between the game's developer and the gaming community.
Here's the long story:
Ninja Gaiden Sigma Plus on the PS Vita remains a beloved action-adventure game, praised for its fast-paced combat, rich storyline, and impressive visuals. Despite its age, the game continues to have a dedicated fan base.