The very massive first stars (m>100 Msun) were fundamental to the early phases of reionization, metal enrichment, and super-massive black hole formation. Among them, those with 140 Msun < m < 260 Msun are predicted to evolve as Pair Instability Supernovae (PISN) leaving a unique chemical signature though their chemical yields. Still, despite long searches, the stellar descendants of PISN remain elusive. We present our PISN-explorer: an innovative tool to catch the elusive descendants of very massive first stars, i.e. to identify candidates for stars with a dominant PISN enrichment. The PISN-explorer is based on a combination of physically driven models, and the FERRE code; and applied to data from large spectroscopic surveys (APOGEE, GALAH, GES, MINCE, and the JINA database). We looked into more than 1.4 million objects and built a catalogue with 166 candidates of PISN descendants. One of which, 2M13593064+3241036, was observed with UVES at VLT and full chemical signature was derived, including the killing elements, Cu and Zn. We find that our proposed methodology is efficient in selecting PISN candidates from both the Milky Way and dwarf satellite galaxies such as Sextans or Draco. Further high-resolution observations are highly required to confirm our best selected candidates, therefore allowing us to probe the existence and properties of the very massive First Stars.