A/N: Naruto is Kishimoto's. Guys, let's make a deal: if you read this, whether you like it or not, could you leave some kind of review? Even one word is enough. Thanks!
"Hate is a bottomless cup; I will pour and pour"
Euripides, Medea
Kagami's house is dark and quiet as he arrives and yet he knows that it is not empty.
He stands in the entrance hall for a moment – a minute, an hour – wishing that there would come the sound of a sliding paper door or of some object falling as a result of a mishap.
In vain. No sound will come.
When he reaches down to unfasten his sandals, he is surprised to find himself holding an unfamiliar leather notebook.
"Congratulations," Tobirama says. "From this moment on, we are no longer master and student, but equals. In honour of this occasion, I would like to offer you a gift. Take your pick of any item you see in my study and it is yours."
Kagami studies the patches on the worn leather, the stains where once an image might have been glued to the cover, the fraying thread holding yellow pages together, the odour of disinfectant and chemicals that clings to the material.
The calm ruptures.
He rips the pages off the book and throws it at the wall hard enough to damage the white paint.
The notebook lays gutted in the corner, pages shredded, but Kagami does not care. His bare feet slap against the floorboards as he runs to the farthest room in the house for shelter.
He slides the door open and freezes, suddenly ashamed of making so much noise. His father is resting.
As has been his routine for years now, Kagami closes the door behind him, before approaching the bed to kiss his father's forehead. Then he lies down next to the man, on his side so that he can study his profile in the slanted light coming in from shaded windows.
Of all of the old man's children, Kagami is perhaps the one who most closely resembles him, physically. They have the same nose, the same thin eyebrows and the same unruly hair, though age has yet to thin Kagami's. This fact has always been a source of comfort, proof of a connection that no one could deny.
"Is he still in there?" five-year-old Kagami asks after his father is brought home from a mission gone horribly wrong. "Can he hear us?"
His mother says nothing. She is crying too much to be able to hear anything that anyone says, much less a little boy's timid question. Kagami's big sister and big brother are both away for the moment, so it is up to him to understand what has befallen his father, while holding his younger brother's hand and pretending that he is not as terrified as him.
The old doctor answers, but it is nothing that Kagami wanted to hear.
"We don't know."
Kagami shifts closer to lean his head against his father's shoulder. He smells dust on the sheets and his mother's favourite rose soap on his father's skin.
The faint rise and fall of the chest beneath his cheek soothes him, but once again that peace is not meant to last. As soon as he opens his eyes, his gaze catches the tiny shards of a round glass phial that rest atop the room's dresser.
"Good choice, Kagami," Tobirama says, holding up the dark wooden rack full of tiny round glass phials of various shapes, each holding one clear portion of fluid. "These poisons will compliment your fighting style well.
"The one that you're holding now, for example, is a particularly sadistic one. I created it over a decade ago, derived from krait venom. The pain as it burns through the nervous system is unbearable. It culminates with the destruction of the victim's brain from the inside, but never fades. Even after the mind is gone, the body will live on and continue to feel it." He points to the leather notebook next to the rack. "Make sure that none of those ever touch your skin. Most do not have antidotes."
Kagami presses his face to the fabric of his father's shirt.
"It was his lab that you were raiding back then, wasn't it?"
He takes a deep breath, letting the scent of dust and rose soap comfort him for one last time, before pulling back. A second glance at the tiny phial on top of the dresser confirms what he already knows. The shards retrieved from his father's body after the accident that disabled him match the design of Tobirama's personalised poison containers.
"You're not in there anymore, are you? You haven't been there for years. Dad... I'm sorry that you had to suffer all this time. We didn't know."
Kagami picks up a pillow and hugs it to his chest.
"...Goodbye."
It is hard to tell when an assassination is over when the victim's body offers no resistance or reaction. Kagami tries to smother his father one time, two times, only to find that he has miscalculated how long a human body could go without air. By the third attempt, he has learnt to wait beyond what he expects to be enough.
He leans his cheek up to his father's nose and feels no breath. It is done.
His eyes sting.
Blood and tears mix as he looks at the world in a new light. The Mangekyou feels strange, both more natural than the regular Sharingan, sharper and more willing to be used, and yet more dangerous, like it is ready to turn against not just his enemies, but against Kagami himself.
His father's old body is aglow with the last remnants of his life energy and Kagami makes himself watch until the last wisps have bled out.
Just before the colours fade to the dead greys of inanimate objects, Kagami hears a whisper in his mind.
"Ka... gami..."
Then the only colour left is the tainted blue of his own hands resting against his father's neck.
"I'll kill him," the boy promises. His voice breaks, but he puts all his heart into the oath. He cannot bear to keep his eyes open anymore, as the tears slide down his cheeks and land on his father's unfeeling skin. "I'll kill him, for you. I know that I'm no match for him, but I swear it, even if it takes me the rest of my life, I will kill Tobirama Senju."