The process involved in converting precursor piRNAs into non-overlapping, contiguous primary piRNAs (approximately 24-30-nt piRNAs with a preference for a 5' uridine (U) via the endonucleolytic activity of cytosolic PIWI. This may include pre-piRNA maturation of 3' ends by trimming and 2'-O-methylation.
primary piRNA processing