After pushing Sasuke and Naruto to the brink of their deaths, Madara made things worse for everybody after absorbing all the tailed beasts inside the Gedo Statue and gaining the immeasurable power of the Sage of the Six Paths. Seeing it's almost time to put the finishing touches on his master plan, Madara flew all the way to where Obito was, seeking the other Rinnegan that would allow him to cast the 'Infinite Tsukuyomi.'
Episode 415 of the Naruto Shippuden anime series is based on chapter 665 (Who I Am Now) and chapter 666 (The Two Mangekyos) of the Naruto Manga Series. Madara, who only needed his left Rinnegan eye to complete the ultimate jutsu that would bind everybody into one entity, arrived at the moment when Obito was struggling to get out of Black Zetsu's control.
For years, Obito had denied his true identity while serving as a harbinger to Madara's path of darkness. However, upon hearing from the elder Uchiha that he's nothing but a mere tool to execute his plan, Obito had finally regained his ninja way of protecting the persons he loved.
When it appeared that he's about to surrender the other half of the Kyuubi inside Black Zetzu, Obito betrayed an unsuspecting Madara and began extracting the yang chakras of tailed beasts inside from his body with the purpose of transferring these to a dying Naruto. Embracing the identity as Obito Uchiha for the first time since the battle of Kannabi Bridge, he teamed up once again with his old pal, Kakashi, with the power of their Mangekyo Sharingan at full strength.
Using their teamwork as their best weapon, Kakashi was able to deceive Madara by using his long range Kamui to teleport Obito to his dimension, where Naruto still in terrible condition. There, Obito started sealing the other half of Kyuubi and fragments of other tailed beast chakras into Naruto's body.
Back in the real world, Might Guy seemed convinced that the climax of the springtime of youth had finally arrived, as he's ready to go full throttle against Madara.