Until We Meet Again

[Tomarry] Harry and Tom, immortal soulmates—thanks to Harry being the Master of Death—decide to do a fun challenge. Tom is back in the 1940's, trying to convince a different Harry that, no, he's not out to murder all muggleborns and make horcruxes. Harry ends up in his sixth year, goes on a hunt for horcruxes with Ron and Hermione, and also makes friends with a very familiar diary.