Timeline:
Beginning during Summer before 6th Year.
Ending after the Battle of Hogwarts.

Alterations to Canon:
The sequence of some lesser canon events may be changed, to suit the narrative.
Specifically Amelia Bones' assassination.

Pairings:
Harry/Tonks.
Harry/Lady Potter (take your pick)
Possibly Harry/Multi/Harem.

Story:
With the death of Sirius hanging over him Harry, at his lowest ebb, reflecting on everything that has happened to this point and will happen with the prophecy he now has hanging over him, decides that he just can't afford the childhood Dumbledore was so insistent that he deserved to have.

People will keep dying until he ends Voldemort. He has to prepare, train and get ready by whatever means he can get his hands on. The longer it takes to do it the more people he will lose. He can't procrastinate any longer, he has to grow up and fight the war that is coming.

Unrelenting nightmares and insomnia along with a lack of any useful training materials leaves Harry with only one way to effectively better himself during his incarceration at the Dursleys, exercise. Running for miles, until he can barely stand and then turning around to run back. It exhausts him enough that every other night he can get a few hours of sleep uninterrupted by dreams.

A few nights after he arrives at Privet Drive, while out on his run, he is brought to a stop by a puffing Tonks, mousy brown hair plastered to her forehead, asking what kind of lunatic runs around in the dark after midnight. Harry feeling no need to lie tells her the truth about why, that it buries the pain and gives him a focus.

Her tender attempt to tell Harry that Sirius' death wasn't his fault, that it was hers, is waved away. Harry knows, he says, that it wasn't his fault, not hers either, it wasn't even Dumbledore's fault for keeping him in the dark or Sirius' fault for doing the only thing he could. Fault is irrelevant. The only thing that matters is that the longer it takes him to kill the Dark Lord the more people who are going to die.

Tonks begins disputing his words but he simply explains that the Order spent the last year guarding the Hall of Prophecy because there is one and Harry's heard it now. It'll end only when he ends it. Tonks is aghast and then sympathetic but Harry bluntly dismisses her sympathy, it won't make him stronger and he needs to be to do what has to be done. Then he leaves her in his dust as he runs back to Privet Drive.

Tonks thinks it over the next day and comes to a decision. That night when Harry is taking out the Dursley's garbage Tonks speaks to him and passes him a box from under her Invisibility Cloak, not keen on getting caught by the on watch Order member.

Harry opens it to find Auror manuals and an assortment of other books on potions, combat skills, stealth, medicine, wards and mind magic. Along with it are 'meal pills' (a full meal's worth of nutrients, for Aurors on stakeouts), Dreamless Sleep, a bottle of fire-whiskey, an old 'Playwizard' magazine and a variety of other odds and ends.

Tonks' next shift is two days later and she lets herself straight into his room. Harry thanks her for her help and now that he's a lot less stressed and healthier he asks Tonks why she looks so depressed. 'I asked a guy out and he turned me down'. Harry's 'Who in their right mind would turn you down?' pleases her just a little. 'Remus, actually'. 'Oh... you think he might be gay?'. Tonks cracks up for the first time in weeks, laughs until she almost cries.

Over a meal of fish and chips Tonks brought with her they talk about how they first met Sirius and Tonks tells him he did the right thing giving Pettigrew a chance... that means that next time he doesn't have to. She, in turn, shares her own first meeting with him and the hilarity that ensued. Desert follows in the form of treacle tart prompting Harry to make a declaration of love, to which Tonks jokingly replies that he needs to hold his horses, it's only their first date after all.

Harry laments that there's no way for him to practice anything he's learned from the books and Tonks, remembering Harry's story of meeting Sirius, says she has an idea. As she's leaving Tonks off-handedly asks if he'd perused the Playwizard yet and Harry blushes and says that the books were more important. Tonks very seriously insists that it's part of the 'assigned reading', all work and no play makes Harry a dull boy.

Three days later Tonks leads Harry out of the house passed a snoring Mundungus - who will sleep the whole day away with a little added spellwork from Tonks - and apparates them to London, flooing from there to the Three Broomsticks and then walking on to the Shrieking Shack. With the existing wards and protections against dark magic and dark creatures plus a few Auror wards for sealing crime scenes there's no chance that the Trace will detect him practising inside.

Harry and Tonks make a list. Apparation (because nothing trumps mobility in warfare), Occlumency and Legilimency, Patronus Messaging and of course Combat. Harry starts out on apparation making decent progress before lunch (according to Tonks, rather than a sceptical Harry), carrying one-word Patronus messages and even fending off some Legilimency attacks. Harry has thought of something else he wants her to help him with. Memories about the Dark Lord and the Death Eaters, they're intelligence on the enemy and surely would be useful to Tonks' boss Amelia Bones, right?

On their trip back Tonks takes him to her apartment first so she can grab the evidence vials from her Auror kit and then takes his memories of Quirrelmort, the Chamber of Secrets, Polyjuice!Barty and the Graveyard... but not the Department of Mysteries. He confesses his attempt to Crucio Bellatrix and Tonks assures him his inability to use it, even on an animal like Lestrange speaks volumes about him.

Back at Privet Drive Tonks sticks around just long enough to spot the Playwizard sticking out from under his pillow. In a tone of voice that eerily mimics McGonagall she asks him if he reviewed the material as instructed. 'Yes, I looked at the pictures of naked witches. Happy?' Harry mumbles. 'Did you look at the centrefold?' Tonks asks, handing him the open magazine. Before Harry can answer she morphs to look like one of the two naked and entwined witches snoging in the picture. 'Tonks! You shouldn't try to make yourself look like one of the girls in this rag!'. Tonks leans in and whispers in his ear that she is one of the girls in that rag. Harry looks between her and the picture and closes the book, red as a tomato. 'Relax Harry! If I didn't want you to look I wouldn't have given it to you!'. She also warns him not to blab, on pain of death. Only he and the witch in that photo shoot with her know the truth... and that's only because the two spent the weekend together afterwards.

A gaping Harry is left-behind by a laughing Tonks as she apparates away. His shower that evening is long, vivid and tires him out so much he doesn't need any potion to get to sleep. Tonks' sleep however is less serene, awoken by a naughty dream about Harry she grabs one of her toys and gives in to the very satisfying fantasy.

Tonks turns the memories into her boss and tells her she needs to see them. A few hours later Amelia takes Tonks aside and questions her. Tonks isn't sure what she should say though and when Amelia says that clearly Tonks has access to Harry and that she'd like to meet with him Tonks decides that Harry at the least should know about the offer. They find a time when Tonks is guarding Harry and Amelia will be free.

Harry agrees to the meet and it happens at the Shrieking Shack, with too much risk anywhere public and even Amelia's own protection detail can't be guaranteed not to report Harry Potter's presence at Bones Manor to the horse-trader Scrimgeour. Amelia, equally as perceptive of Kingsley's 'other job' as she is of Tonks, uses him to slip out of Bones Manor without her detail for the meet.

Harry and Amelia meet, all off the record, so to speak. Every little detail of the memories is analysed and more that Harry can recall (i.e. Draco's bragging about the concealed door under the floor at Malfoy Manor) including even the facts of the prophecy, if not the wording. Amelia shares her own suspicions about something, the Diary from the Chamber Incident. When she was made the Head of the DMLE she was briefed by Unspeakables regarding magic so forbidden that there weren't even laws on the books so that people would learn such magic existed... things like a Horcrux. The three make some excellent deductions about the significance of how the diary worked and that its destruction didn't end Voldemort but Amelia thinks she needs to ask the Unspeakables for more information.

As they are about to wrap it up Kingsley's lynx Patronos arrives warning her that Bones Manor was attacked and to get to safety. Tonks and Harry lead her down the tunnel to the Whomping Willow so she can get to Hogwarts, they have to get back to the Dursleys pronto, something like this will mean an Order meeting. While they wait they practice Harry's Occlumency and Tonks briefly gets a glimpse of his shower fantasy where her unmorphed self was the one in the Playwizard centrefold, much to Harry's embarrassment and Tonks' amusement (and secret delight). When the Phoenix Patronus arrives Tonks takes Harry with her - 'can't leave you unguarded, with the Dark Lord assaulting homes, can I?'.

A New Normal:
- Amelia at Grimmauld Place 'surprised' to find another Auror (Kingsley is already there) working for Dumbledore when Tonks walks in.

- Harry and Tonks go on what is nothing less than a dinner and a movie date before returning to Privet Drive. Best date Tonks has ever had, without any alcohol at that!

- So much time away from the Dursleys delay the ward recharge postponing Harry's relocation to the Burrow but provides additional time for Tonks to continue secretly training Harry.

- A waiver from the Reasonable Restriction courtesy of Amelia.

Decidedly Not Normal:
- A letter arrives from Gringotts to inform Harry that Sirius' Will was challenged and invalidated by the Malfoys and that he will need to appear before the Inheritance Tribunal to make his claim to the Title, Estate and Assets.

- Retaining Tonks' dad as a lawyer Harry finds a bylaw in the Black Family's rules of inheritance, that with the end of the existing main branch that the status of becoming the new main branch will be given to the remaining line with the 'greatest claim to Black Blood'.

- Harry and Tonks together would possess greater claim to the Black family tree than Draco Malfoy and any other witch. A betrothal contract throws Tonks for a bit, not how she imagined things going with Harry... but eventually she agrees. Harry successfully wins the title of Regent Lord Black, having until he is 21 to sire a child by the new Lady Black otherwise the title shall pass to Draco.

- Tonks, having had quite a few thoughts about Harry already, finding herself married and with no honeymoon in sight, declares that as his wife she at least has the right to a wedding night and Harry's virginity.

- Before Harry goes off to Hogwarts Tonks tells him he better not be shagged out next time she sees him. Harry is confused and a little bit hurt, he's not going to cheat on her. Tonks, realising that sometimes Harry can still be as clueless as ever (good thing that's something she finds attractive about him), explains that she's the Lady Black, her children will be Blacks. If there's ever to be any future Potters he better get a move on and find himself a Lady Potter. Tonks also makes it clear it would be in his interest if the other wife suits Tonks tastes too... including in bed.

- Covertly independent Harry playing the field at Hogwarts amongst chunks of derailed canon plot dropping in to stir things up with occasional visits from Tonks, such as Hogsmeade weekends.

The Lady Potter:
Word of Harry's acquisition of the Black line through his betrothal to Tonks leaks to the press. Witch Weekly headline: 'Potter to Wed! But Don't Worry Ladies... He Still Needs Another Wife!' resulting in lots of girls angling to nab the chance to marry such a politically influential and rich wizard, alongside girls who already and actually like him.

Who wins the day? A plausible winner, preferably: Hermione, Ginny, Luna.
For added comedy/drama: Susan. What would Amelia think of Harry and Tonks dating her dear, sweet niece?