He decides to walk tonight. There are more convenient ways to travel, but his sharingan is spent and his chakra is thin, and it is not the first time he has traveled like this. Though slower and more cumbersome, he does not mind walking. In fact, he prefers the smell of dust and sun-burnt earth to the Kamui's gaping emptiness, how the darkness around him is dotted with punctate stars.
Around him, the darkness stretches, and the land is bare except for the rocks and scattered trees dotting the craggy landscape. As a child, he had no idea what he would see, crossing oceans and mountains and watching civilizations be razed and spent, the smell of dead bodies littering the ground.
But there is no such thing as loneliness, when conviction and purpose light his way. Darkness rolls, and Obito pulls back the hood of his cloak, walking forward.
"Tobi! You're back," Zetsu says, but the plant has a worried look on his face, moving physically to block Obito's path. "We were not expecting to see you so soon! Maybe you should wait a moment," Zetsu says, but Obito pushes Zetsu out of the way, entering the mouth of the cave.
Obito stops, then turns. "What is it?" Obito says, and Zetsu's face looks more pale than normal.
"Kabuto did it," Zetsu says. "He said he was doing an experiment-"
Obito shoves Zetsu back, then steps forward.
The door opens. Obito's eyes widen.
"Tobi! Tobi! We tried to stop him!" Zetsu rushes behind him and skids to a halt, while Obito stands at the doorway, a barely contained rage bubbling at the back of his throat. "He said he was doing an experiment, he said he was perfecting the Edo Tensei-"
"Where is he?" Obito says.
"I said, where is he?" Obito says, and Zetsu yelps, jumping back.
"I don't know!" Zetsu says, but Obito activates his sharingan, searching for the trail to Kabuto's chakra.
Behind him, Zetsu glances back at the bedroom nervously, watching as the woman with the brown hair starts to breathe.
The door to Kabuto's lab swings open. "Ah," Kabuto says, and he rises. "I see you have found my gift, Uchiha Madara-san."
His arm slams into Kabuto's throat. Beakers rattle, Kabuto slamming heavily against the bench.
"Release it," Obito says.
"Release what?" Kabuto's voice, though strained, is infuriatingly calm, and Obito squeezes his grip tighter, making Kabuto wheeze.
"The Edo Tensei. Release it," Obito says. Kabuto looks up at him and grins.
"That would be unwise, Uchiha Madara-san. If I release the technique, your army will be cut too thin-"
"Release it on her," Obito says, and he lets go of Kabuto's neck, Kabuto's body dropping to the ground.
Kabuto coughs, then winces, rubbing the front of his neck. "I would have thought that you would be pleased," Kabuto says. "My little birds tell me all sorts of things. I would have thought you'd thank me for my generosity."
"I told you," Obito says, and his eyes narrow. "Release the technique now, or else I will peel back all the layers of your scaling skin."
"Come now, Uchiha Madara-san. We need not resort to needless violence." Kabuto slithers upwards, grinning. "That technique is different from the Edo Tensei. I couldn't release it if I tried."
Obito's eyes narrow. In all the years he has spent leading the Akatsuki and Bloody Mist both, he has learned the value of patience, especially when dealing with the lot of errant men. Minor, petty annoyances. Evidently, Obito's silence is permission for Kabuto to speak; he crawls, grinning and oozing guile, as he rises back onto his feet.
"I see you are wondering what it is I did," Kabuto says. "As I said, it was an attempt to perfect the Edo Tensei," Kabuto says, and he smiles again. "Let's just say it was an application of light and dark chakra, much like that Rinnegan in Nagato's eyes. It was, shall we say, an elegant piece of work," Kabuto says, smiling. "I am actually quite proud of myself."
"Why?" Obito says.
"You would have to get more specific than that," Kabuto says. "There are many answers to the question, 'why.' Like perhaps the answer, 'why not?'"
"Why her?" Obito says.
"Funny you should ask that. And here I thought you would be happy, reuniting with your long, lost love-"
The blow that comes knocks Kabuto off balance; the second one slams him forward, pitching him to the side.
"You can't kill me, Uchiha Madara-san," Kabuto says. "I am the one controlling the Edo Tensei. Without me, they cannot be stopped."
"I no longer care about the Edo Tensei," Obito says, and Kabuto's eyes widen.
The room explodes in smoke, and suddenly there's nothing but sound and vibration, Kabuto's voice floating through the air.
"Forgive me, Madara-san. But as you can see, I'm rather found of my snake's skin."
Obito grits his teeth. Genjutsu. It paralyzes his body and blinds his eyes.
When the smoke clears and the vibrations cease, the room is empty, and Kabuto has suddenly disappeared.