Time Traveling Marauder

When Sirius goes through the veil during the battle at the ministry, he switches places with his twenty-two-year-old self who had been in Azkaban for the last six months. But time travel isn't as precise as one would think. Things get interesting when a younger Sirius steps out of the veil and into Hermione Granger's arms, three years after Voldemort's fall. Post war. EWE. Smut.