This is a tribute to the one type of Snarry that I read. Time Travel Snarry. Whether it's Harry traveling back to the Marauder's era or being sent there by accident, and growing up there to become friends and possibly more with a younger Severus Snape. Another version that I like is when Harry travels back to raise or help his past younger self and becomes friends/allies/later more with a Snape that he better understands/is the same age as now.
So yeah, here's a Marauder's Era version of that.