Oh God, Not Again! By Sarah1281

Adult Harry Potter accidentally goes back in time and wakes up on his 11th birthday again, but with all his memories of the future intact.

Masquerade¹ → Tom Riddle ✓

When Evelyn returned for her Fifth Year at Hogwarts, she expected everything to be the same. But when Dumbledore gives her a task to infiltrate Tom Riddle's gang, to steer him from his current path, she finds herself drowning in dark magic, surrounded by a boy with a constant masquerade. ---- Unravelled is the sequel...