"Rehabilitation" (リハビリ, Rihabiri, Viz: Rehab) is chapter 603 of the original Naruto manga.
Left to the company of White Zetsu and another with a spiral-like facial pattern, Obito becomes thoroughly annoyed at the duo, who are fascinated with how human bodily functions work — not having the need themselves to eat, drink, or even use the bathroom. Telling them not to lump him in with their lot, Obito notes that only half of him was made of artificial material. Stating that they were supposed to help Obito with his rehabilitation until Madara woke up, the duo began to question Obito about why he kept repeating a bell sound and "stupid Kakashi" during his slumber. After explaining that the third clone had gone outside to gather information and that they were able to move through the earth, the two Zetsu begin to recite Madara's plans for world peace. Disregarding this, Obito once again states his resolve to leave this place and join Rin and Kakashi, thus began his painful rehabilitation while remembering his time with Rin and Kakashi with his memories being trying to kiss a picture of Rin even after taping out Kakashi's face and later after training trying to give Rin a signal that he loves her, only for Obito to discover much to his annoyance that Rin was looking at Kakashi, not Obito. After one training incident that leaves Obito suffering from a wound in his hand, Rin patches him up and tells him it's not good of Obito to hide his wounds because she's looking after him. In the present and after what seems to be a fair amount of time passing, Obito, whose hair has noticeably grown longer, is able to use the artificial limbs perfectly. One day, White Zetsu returned to the hideout and alerted Obito that his comrades were in danger, surrounded by Kirigakure shinobi. Leaping into action, Obito tries to break out of the cave, but only manages to crack the rock and tear off his right arm. The spiral-patterned Zetsu offers up himself as a suit of sorts and encases the young Uchiha, who prepares to head out.