A/N This will work better if you've read the prolouge. Nevertheless, the first few chapters will still be mainly setting up for the first arc.
Bellatrix locked herself in Hermione's bathroom, picked up her dress so she could climb into the empty bathtub, and sat down. This was not a first though it was unusual, more often she tended to go into the garden to get some space and clear her head before making important decisions. Hermione had just dropped one helluva bombshell. Unfortunately Bella couldn't stop her thoughts from drifting back to a certain brunette Gryffindor who had been occupying more than her thoughts recently; she wasn't a fan of this recent addiction that she was developing. It was the third night she had slept over at Hermione's, and it had felt completely natural.
She thought back to the years before they had met, before the end of the war. It's easy to become accustomed to the cold. It starts to feel less and less cold, until you barely notice it. The way the icicles hang and the frost glazes over the tough surfaces and smooths the rough edges, all creates such a sublime illusion, which Bellatrix was happily taken with. Or at least she had been.
In a similar way, it's easy to become accustomed to the heat she thought. The warmth some people just seem to bring with them when they're near you. When you start to feel the heat again, after acclimatising to temperatures below freezing, it's a welcome shock akin to returning home before you even realised you were homesick. Bella smiled slightly, Hermione's prescence made her feel more at home than anything had ever done. Tom had come close once, but then he had drifted away too absorbed in his plight and lust for power to pay proper attention to her, she scoffed at the now distant memory.
Another side of Bellatrix started to argue against this keen towards domesticity. Once you snuggle up and wind down, absorbing the heat through every pore and letting yourself go into the relaxing warmth; it welcomes you in a manner too affable to resist, and on more than the odd occassion - if you're unlucky - the temperature keeps going up. You're so busy getting comfortable you don't realise this sauna's turning into a volcano. She sighed, thinking that she would be a Gemini according to those silly muggle horoscopes Hermione had been reading recently. The side that wanted her to run pushed at her harder, painting a picture where the heat reaches a level close to unbearable. If it had been this hot earlier you would never have gotten in, but now you've already adapted to such heat a mere few degrees beneath this, so maybe you don't even notice. Your skin turns red and the welcoming warmth turns a little too hostile, a little too aggressive in its welcome. The suffocating heat continues to rise, and it's when you come back to Earth from your daydreaming state that you realise it's a little too hot for your liking.
Her heart started to join in the argument; don't you recall that infernal cold. Don't you remember how your hands felt stiff and your knees ached, your fingertips froze and you were too afraid to lick your lips for fear your tongue would stick to them. Stay in the heat, this overwhelming heat, to avoid the cold. It's better to maybe boil later, than get up and get out now.
Because you don't realise it's slowly killing you, her head retaliated. The heat won't stop til it passes boiling point, and you won't survive that long. But we will fight to survive, we will fight to acclimatise to this new heat, as it keeps on increasing if you insist on staying with this... this girl. Maybe you'll realise soon enough. Maybe you'll fight to stay alive hard enough to make it. But maybe the heat will get too strong, be too intense. You've been broken by this before, so take care with this a source of warmth. You may think it's better than the cold, for now.
The logical side of Bellatrix, satisfied that her heart was doubting Hermione, stopped with that mic drop moment and waited for Bellatrix to reach a decision.
Bella barely paused for a moment, before climbing gracefully out of the bathtub, turning around and marching into the living room, their living room.
Hermione's eyes flicked up over the top of her book "You were gone so long I thought you'd..." Hermione didn't have the chance to finish that sentence as Bella's lips were on hers in the rare kind of kiss that expresses pure love. Bellatrix broke away, and looked into Hermione's eyes "Yes." She kissed Hermione again.
"Yes, I want to move in with you."
A/N So the scene is set. Reviews are much appreciated and will be rewarded with my eternal gratitude.