Finally (やっとだよ, Yatto da yo) is chapter 640 of the Naruto manga.
With Minato unable to teleport to Naruto and Sasuke's aid because the mark that was previously on Obito had seemingly vanished, things looked dire for the two. Naruto, however, remembering his father's explanation of how his technique works, uses chakra arms to grab onto both Sasuke, and his father allowing Minato to teleport them to safety. Thoroughly impressed by his son's action, Minato and his group turn their attention back to Obito in time to see the new jinchūriki losing control of the beast once again as his body begins to become distorted. As Obito launches a compressed version of the mysterious substance, Minato prepares to deflect the projectile, but to everyone's shock, the attack stops short of them, expands and then contracts before returning to Obito. Thinking that the attack was meant for Minato's shadow clone, they soon realise that Obito was struggling to maintain control and the previous attack was an attempt to destroy the out-of-control portion of his body. Intent on launching his counter-attack, Minato instructs Sasuke and Naruto to follow up with a collaborative attack right after. During this time, Obito — who is only able to utter Rin's name at this point — struggles to maintain his consciousness and with it, the control of the beast. As Minato, remembering the young man he had trained years before, rushes to aid him, in Obito's subconscious, Obito focuses on an image of his old team as the Ten-Tails attempts to rip his consciousness apart, Obito is ultimately able to seize control of the beast, emerging in a form even more reminiscent of the Sage of the Six Paths' silhouette inclusive of a shakujō. In full control, Obito attacks Minato, tearing his arm off, forcing the Fourth Hokage to teleport a safe distance away. However, their safety is proven to be nothing but a ruse as Sasuke and Naruto noticed that Obito had attached some of the mysterious substance to Minato's reconstructing body. In shock, all those around them look on as the ball began to glow, preparing to expand as it had done before.