HP: The Dark Arts Ace Younger Sister of the Savior's Family

Content warnings:

1. After Voldemort's defeat, he is reborn as Potter's “sister.” The story involves a gender swap, though he changes back later.

2. The pairing is with the Professor, and Voldemort is the top. This is non-negotiable!

3. Voldemort will transmigrate into magical worlds at unpredictable times (including, perhaps, The Ugly Duckling, Cinderella, Snow White, and his own childhood...)

Serious synopsis

He once arrogantly sought to become a king who looked down upon the entire world.

He once

stubbornly declared that he had never feared anything.

He once scornfully trampled upon the love he considered worthless...

But in the name of love, a flash of green light brought him down. After lying low for years, he emerged from the cauldron with a new body, thinking at last he could fulfill his grand ambitions, only to be defeated once again by the same little brat, still wet behind the ears. Those people raised the banner of justice and said to him proudly, “Why did you lose? Because you don't understand love. You never have.”

The Dark Lord knew everything, but this time he had to admit that he didn't understand. His shattered soul was rejected by Merlin, and as he struggled at the gates of purgatory, he still refused to admit he was wrong.

...“You will learn to fear,” a voice told him before he left purgatory. When he opened his eyes again, would he find a new beginning or destruction?

P.S. All the first-person narration in this story consists of Voldy's inner commentary.

The fairy-tale worlds may take a while to appear. The first one begins around Chapter 6 or 7, and progress is slow because the goal is to increase his absolute power.