Harry Potter's Book of Sins

When a time-traveler mistakenly believes he has traveled back to 1980s England, enduring childhood hardships and eventually sinking into darkness, a strange yet familiar letter of admission reignites his life.
But when he encounters deeper darkness, will he choose to stay away from the abyss or dive into it without hesitation?
"Just wait, I'll be back soon."
At a certain bedside on the fifth floor of St. Mungo's Hospital, he finally firmly grasped her pale hand.
This is a story of a little trickster who grits his teeth, deceiving even himself, as he struggles repeatedly between pain and tenderness.

Long Chapters! 2698 Chaps total!

Translator's Synposis : MC is an orphan, hufflepuff, and schemer. No cheat other than being super talented. He researches potions of his own, doesn't care about the difference between light and dark magic.