Slightly AU; In canon, Lupin is first introduced in 1993, when Harry's in third year. This is set in 1990, when Tonks is in seventh.
"Remus, good to see you, come in," Andromeda Tonks welcomed Remus Lupin, who she had first gotten to know when she had been Head Girl at Hogwarts School of Witchcraft and Wizardry and he had been a lowly first-year. They had been in what were largely fiercely rivalling Houses, although Andromeda had been somewhat misplaced in Slytherin and mostly preferred hanging out with her younger cousin Sirius and his friends in Gryffindor. Because of that, she had been one of just six people who had known that he was a werewolf (eight now, including her husband and daughter). It hadn't bothered her in the slightest. He had been a caring, thoughtful boy who took great pains not to expose anyone to the darker side of him, and that was a hell of a lot more than most people tried to do – full-humans who ought to have been able to help themselves. Her own sister Bellatrix for example, who was currently rotting in Azkaban for various offenses, Bellatrix had been considered cruel even for a Death Eater, her career culminating in the mind-frying torture of a gifted and well-liked Auror and his wife, effectively leaving their son an orphan.
Compared to Bellatrix, Lupin was a saint, and not one that she was going to refuse entry into her home for being a werewolf.
Lupin entered the house. "Nice place," he said, a little enviously. The fear and discrimination directed towards werewolves and other half-breeds meant that it was very difficult for him to get a job and subsequently afford a nice place like that.
"Nothing I really earned," Andromeda admitted. "Dad's will was such that it couldn't be broken. Though I'm sure if he were alive, he'd take Bellatrix over me."
"Then he's an idiot."
Andromeda smiled at what was Lupin's obvious sincerity. He would never have been admitted in her father's house, but he was a much greater calibre of man than she would have known there. "What brings you here?" she asked.
"I wanted to talk to you and Dora, actually," he said. Andromeda led Lupin into the living room and called her daughter Nymphadora, who rarely answered to anything but her last name. Her parents and Lupin were among the few exceptions, and even they were only allowed to call her Dora.
Tonks came into the room wearing, as usual, torn jeans and a tight white t-shirt featuring the Weird Sisters. "Remus!" she said, smiling to see him. He was the only one of her parent's friends whose company she enjoyed.
"You look good," he said, always pleased to see her. She was a sweet girl he'd known from babyhood and very mature for her age. He suspected part of it was because being a metamorphmagus – a shape-shifter of sorts – had taught her a lot of lessons about how many users there were out there – so many boys who wanted to be with her only because she could be any fantasy – and the value of true friendship. "I'm glad you're here so I don't have to say it twice. I've been offered the position of Defence Against the Dark Arts teacher at Hogwarts."
Tonks beamed. "Oooh, Remus, that's great!" she enthused. "It'll be so good to have a mate as a teacher. All the DADA professors we've had so far have sucked."
"That's why I came to talk to you before I accepted. I can't be your friend at Hogwarts, Dora. And you can't say anything about my – er – condition."
"You mean being a werewolf?" she asked, completely upfront, as always.
"Yes, I mean being a werewolf. The staff knows, of course, but Dumbledore agrees that parents just won't understand so it's best not to let them or the students know, except you and your folks, of course. I'll understand if you think you can't keep a secret, or if you don't like the idea of me teaching her, Andy, but I thought I'd save myself the trouble and clear it with you guys first."
"Of course it's doable, Remus," Andromeda said. About bloody time he had a decent job, too, she thought. "Dora?" she asked pointedly.
"Yes, of course – I won't say anything – or treat you like a friend – if you don't want me to."
"I appreciate that. And we can still be friends – just not while I'm trying to be your Professor." Tonks smiled winningly at that. "So brace me. Tell me anything I should be wary of."
"There's a Malfoy in our year – one of Uncle Lucius's nephews," Tonks said, making a face. Though Richard Malfoy shared his uncle's opinion about anyone who was less than a pure-blood, he had a fascination with the girl he referred to as his 'cousin' for the way she could change her appearance at will. As if Tonks wasn't by this point excellent at deflecting unwanted male attention. She had known from an early age that there would be a never-ending line of men who wanted her because she could be any fantasy and not for her. "And mum never believed that Snape really turned good. He teaches Potions."
"I heard," Lupin said dryly. Dumbledore didn't trust Snape with the position he really wanted – the one he was going to teach himself. He had his own history with Severus Snape; the man had been arch-enemies with two of his best friends, James Potter and Sirius Black, and Lupin doubted that the fact James was dead and Sirius in prison would soften Snape's attitude towards him; Snape had born a grudge not only against James and Sirius but Lupin and another friend, Peter Pettigrew – now dead – and was unlikely to have let it go. "I can deal with Snape."
"He doesn't like anyone who's not in Slytherin," Tonks said. "Gave me a totally filthy look when I didn't end up there, as if I'd want to go. Besides, they don't take half-bloods."
"Tell that to Snape – his dad's a muggle," Lupin said. Tonks chortled gleefully at that information. "Don't go spreading that around, please. I'm one of the few people who know that so he'll trace it back to me easily enough if it gets back to him. Though you're right, the Hat tends not to sort half-bloods into Slytherin. How Snape thought Lily Evans would get in, I'm not sure. I would have been floored if you'd gone anywhere but Hufflepuff, to be honest." Her dad was a muggle-born wizard who had been sorted into Hufflepuff, and since students tended to be sorted by families and Andromeda had been a – somewhat misplaced – Slytherin, it was natural for Tonks to end up in the same house as her father.
He ended up staying for dinner and reluctantly Appirated back to his own apartment in the early hours of the morning. "Poor man, he must be so lonely," Andromeda mused. "He took James and Peter's deaths so badly. And Sirius..." It was hard to tell what had been worse, the deaths of two of his best friends or the fact that the third was responsible for their deaths. "I'm glad he's been given this position. It's so hard for him to find work and it can't be good for him to sit at home all day feeling sorry for himself."
"Yeah," Tonks agreed. Lupin fascinated her. He was the most well-read person she had ever met, with a desire to learn that bordered on fanatical. With an insight that beguiled her age, she thought it was because he'd had to fight so hard for the right to get an education in the first place. Even though they couldn't be friends during class, she still looked forward to seeing him at school.