He'd seen her through the Weasley girl's eyes. He'd seen the mark on her left wrist, recognized it as the twin to his own, and decided in that moment that the Weasley girl was no longer of use to him.
Yin. The shape was dark against her skin and stood out despite its sun-kissed canvas, mirroring how Yang was scarcely noticeable against his wrist from a distance, except for the small circle of Yin within it. The small bit of Yang, starkly standing out in her mark, fueled his determination.
It took a few weeks for his hold on the Weasley child to strengthen enough to talk to his Yin. Despite her youth she was distrustful. Despite using her young friend as a puppet, she was guarded as he made the Weasley girl lead her to him.
He made sure the stunner was gentle, made sure his basilisk brought her to him with great care.
He knew about his older self. He'd lost his mind with age, lost his body to an infant, and become a madman. But if he was careful, Tom could win. If he was careful, she could revive him.
The Weasley girl fell unconscious as he used her energy to take a corporeal form. Yin was unmoving against the flagstone and her cheek felt cold to his touch.
She was so small.
The stains on their wrists lined up.
A spell and the press of his lips to her mark bound part of his fractured soul to her skin, just enough to compel her to keep his diary until she trusted him. He needed time to overwhelm his older form, time to put himself back together. Time for her to grow.
He put his diary in her hands and altered the Weasley girl's memory.
"I will be with you always," he whispered against Yin's cheek. "Write to me, little one."
He used Weasley once more, just to return them to the upper levels of the castle. When they awoke, they'd think the Diary was Yin's. When they awoke, they'd merely go about their evenings.
When she awoke, she would write to him.
The first year, he learned her. The second, he began to teach her. The third, he shared part of his plans with her.
His older self terrified her, attacked her friends, made her fear him.
Still, she wanted to go to the ball with him, and became depressed when she realized certain enemies of theirs would recognize him. He led her to the Room of Requirement instead. It let him see her. He could touch her again.
Her cheek was warm this time, her bright eyes open.
"You're so small," he told her, smiling when she glared at him. He brushed his cheek against hers and held her near. "I like it."
He knew what her handwriting looked like when she was in a righteous fit, but seeing the fire in her eyes as she tried, and failed, to intimidate him while he ignored her scolding made a smirk tug at his lips. He shushed her, complimented her dress robes, and toyed with some of the periwinkle material curiously. He watched her squirm, only growing distracted when she bit her lip nervously.
"Do you trust me?" he asked. "You're wary of my counterpart, but do you trust me."
"You're the same person, technically," she whispered.
He reached up to toy with her curls. She'd tamed them until they were silky and feather-soft. Something on her smelled sweet, like vanilla and orange oil. It filled his lungs and settled in his chest. Without thinking, he pressed his lips to her hairline.
"You didn't answer me," he murmured.
Their noses brushed. He chuckled when her breathing changed.
"You're him," she managed to say. "He's evil."
"He isn't me," Tom stressed. "He put all of his sanity, his stability, put me, in our diary. He won't win." His thumb traced the rosy hue across her cheekbone. "World domination is a fool's ambition. He isn't playing the game. He doesn't even have all the pieces…"
"Do you?" she asked.
"Not yet, but I know where they are." He ghosted his lips across hers and drank in her quiet noises of frustration. "Help me put myself back together, little one, and I can end him. You want me on the outside instead of him, don't you?"
He heard her swallow apprehensively. "I want you to be good."
Tom frowned at her words. "As long as I'm winning," he said vaguely, "for you, little one, I would try. We will win."
Her wide, doe-like eyes stared at him until discomfort stirred in his chest. It was as if she saw through him. As if she was actually considering denying him. "Do you promise?"
He resisted the urge to roll his eyes. "To play by the rules when I'm out?" he asked. "To be good?"
"You can't be evil," she said softly.
He sighed, resigned. "I reserve the right to do whatever necessary to put us at the top," he said carefully. "But I promise to keep the murder and torture to a minimum, and to not get caught."
She echoed his sigh, but he could see in her eyes that he'd won. He rewarded her with a proper kiss.
"Don't fret, little one," he murmured. "Only the people who stand in my way will suffer."
She tasted like sugar quills and butterbeer from her brief dip into the festives in the Great Hall. He played with her hair even after she called him annoying for it, marveling as the clumps of curls slid through his fingers like silk.
"You'll come up here more often," he said, tasting her lips again when she agreed.
Toying with her hair never got old, even after it stopped irritating her.
The fourth year passed. She helped him find the diadem, held him through the torment of reclaiming a fraction of his soul, and kissed him when it was over.
"I've got you," she whispered against his skin. "You're still good."
He didn't correct her. He wasn't good, not like her. But he could play the game. He could tweak his plans so they didn't upset her.
His other self lured her and her friends to the Ministry, and he didn't hear from her for weeks. He could feel her weakness. He felt the curse hit her as if it had hit himself, recognized it as a spell of his own invention, and started to realize why she was so adamant that he be good.
Her writing was shaky when she came back to him. She tried not to visit him in the room again before her summer break, but he was persistent. He wanted proof that she was fine.
The scar made him livid. It made him hurt.
"I'll kill him," he swore.
She wouldn't look him in the eye. "You tried to kill me too."
"He tried," Tom seethed. "I would never."
He kissed her tears away and managed to heal the scar more than the school nurse had. It was still there, still raised and puckered in most spots, but it wasn't the bruise-like purple and pinks it had been when he'd started. It was paler. He traced it with his lips until her tears stopped.
"I'll be better," he promised. "You'll be safe when we've won."
The fifth year, things got worse. Even now, Dumbledore was in his way. He needed his pieces, but he couldn't lead her to them easily.
"He's sick," she told him. "Something is wrong with his hand."
Tom's smile was mean. "Old fool."
He helped her steal his ring, thankful that Dumbledore hadn't quite figured out how to destroy it, but hesitated to bind his soul back together.
"Remorse feels terrible," he told her.
She held his hand and gently placed the ring on his middle finger. "I need you whole," she said. "I'm here."
He grit his teeth through the pain, but this time it overwhelmed him. He woke up with his head in her lap, tired, weak, and shaking. Angry. But he felt like more of himself.
He kissed her worries away with more aggression than he meant to, but she only sighed and relaxing into his touch. He nipped her lips, grazed his teeth along her jaw, and left a mark against her shoulder.
He murmured, "Tell me when to stop," against her collarbone. Then, "Tell me you're not ready," against her ribs.
But all she said was, "Please."
Dumbledore died when Tom only needed three more pieces of his soul.
His locket. The Potter boy. His other self.
She went home for the holiday. Dumbledore's Order brought her in for their meetings.
The Potter boy tried to sneak off on his own. Tom prepared her to keep the three of them alive.
Without the Room of Requirement, he was left with only her words. He couldn't heal her injuries after run ins with Death Eaters. His patience was thin, but he had to wait.
Once he was whole she'd never leave his side again.
She managed to fuse the piece of his soul in the locket into the pages of the diary and for the first time, Tom suffered alone. Woke up alone.
He begged her to sneak into Hogwarts, but knew, even as he wrote the words, that she couldn't.
I'm sorry, she wrote.
You'll make it up to me, I'm sure, he'd written back, trying to keep his hands from shaking and not quite succeeding. Just win, little one.
They stole from Gringotts and returned to the school. She knew they wouldn't find the diadem, but the Potter boy was desperate. She got caught transferring his soul from the cup to the diary, and shocked him when he learned she'd obliviated her own friends.
Ron doesn't listen and Harry…he's got enough to try and sort out. It was the only way…
She told him his other self had a snake, Nagini, and that it was probably a horcrux as well. Tom did the math, scoffed at the number, and told her it could be ignored. Killed even.
Over time, she would fill in whatever gaps were left, minute as they would be. He just needed a body. And he'd prefer not to have the Potter boy walking around with the ability to telepathically connect to him.
Granted, she'd described his other self to him, and he wasn't certain he wanted that body.
If you're whole, or whole enough, we can fix it, she'd speculated. I rather like your nose.
I think I could deal with the nose if I had hair, he told her. But I'd rather look like myself.
She went quiet.
He could feel her heart beating. She had his diary with her.
He felt it when she neared other pieces of him. One of them passed through the pages and it was the first time the pain didn't overwhelm him.
Harry realized my tattoo matched yours…well, his, I suppose. He is giving us a chance to retrieve our wounded…and the dead. Harry and I went to the Room to talk about it. He said he trusts my judgement. Conditionally, at least.
Tom's eyes narrowed. What's the condition?
That if…if I manage to bind you to him and…and he wins instead of you, that'd I kill us both.
Hermione- he began, but she kept writing.
You're not him. He's evil. You're…self-serving. And right now serving yourself means being better. But if you aren't the side in control, then we've lost anyway.
He didn't like the thought of losing. He certainly didn't like the thought of losing to his pathetic counterpart, of dying without seeing her again. He hadn't held her in over a year.
We'll win, he said. I'll make sure of it.
She stopped replying. Nerves prickled against his neck.
He didn't like waiting. Or being in the dark.
It startled him when something finally happened. He felt her pull him from the diary, and, though he didn't know how she managed it, push him towards his other self.
There was rage, then suffering.
And then everything went dark.
There were fingers in his hair.
His eyes hurt when he opened them. When he tried to move his head, he realized everything else hurt too. But he was in her lap. Her arms were around his shoulders as she hunched over him and cried.
"Little one," he said, his voice rough. "Sh, I'm here. We won, little one, we won."
The Potter boy vouched for him, kept her allies from killing them. "Voldemort was Tom Riddle," he said, "But Tom Riddle isn't Voldemort."
The snake, the fraction he hadn't cared about, was killed. It added to his weakness, but she was still strong. And the first time he looked in a mirror, his reflection wasn't a monster. He had a nose. He looked seventeen. She's smiled at him.
There was a formal trial. He played their game.
A mind healer from St. Mungo's went through his head and hers. They played the game.
They asked him why they should believe he changed. He looked at her with the smitten expression they were looking for. He wondered how and why his other self had fallen so far when the games were so easy.
"Voldemort didn't have her," he said. "I do. I have for years. Could any of you be less than what your mate needed? Do you any of you think that she would need a monster like he was?"
They put him on house arrest for two years and showered victory spoils upon his mate for, effectively, ridding the world of Voldemort.
Gaunt manor, an abandoned, decrepit property lost deep in Wiltshire, was rebuilt and restored. Tom's laughter echoed around its halls the night they moved in.
"You promised to be good," she reminded him. He could hear the amusement in her pitiful attempt to scold him as he relieved her of her robes.
"I promised to try," he said. "And to not get caught."
His smile was predatory. "We will win. You don't worry your pretty head about the games I have to play to do so."
She huffed at him, but turned a blind eye to most of his "house calls" anyway. He rewarded her with tenderness. And when he was sloppy, forgetting silencing charms when irksome wizards spoke out of turn in his presence, he kissed her discomforts away.
He got a job at the ministry when his parole ended, and left his games to after-dinner meetings.
It took a decade for people to forget that Tom Riddle had anything to do with Voldemort.
And that was their first mistake.