The prefix (e.g., "NSPS") identifies the production label or a specific thematic series.
Since NSPS-306 is a compilation release, it serves as a "greatest hits" package from the label's archives at the time. nsps306 matsuno yui kirihara azusa uehara yu
Given the structure, it seems like you're referring to a paper authored by Matsuno Yui, Kirihara Azusa, and Uehara Yu, possibly with an identifier or code of NSPS306. The prefix (e
: The title is primarily distributed via digital platforms and DVD collections. The prefix (e.g.