Required during spermiogenesis to participate in the repression transposable elements and prevent their mobilization, which is essential for the germline integrity. Probably acts via the piRNA metabolic process, which mediates the repression of transposable elements during meiosis by forming complexes composed of piRNAs and Piwi proteins and govern the methylation and subsequent repression of transposons (By similarity). Localizes to chromatoid body (CB) and pi-body (also called intermitochondrial cementin), 2 cytoplasmic ribonucleoprotein granules involved in RNA processing for spermatogenesis. Belongs to the TDRD5 family.