Naruto Shippuden 422 begins a two-part filler special where we follow the story of Konohamaru as he develops his own type of Rasengan from scratch and uses it against Pain. Naruto goes in and out of missions while Konohamaru directly concentrates on developing his Rasengan while using his sexy jutsu.
Naruto Shippuden 423 is a filler episode concentrating on Naruto and Konohamaru during the time when Naruto was training in order to defeat Pain and the Akatsuki. While we mainly concentrate on Konohamaru and his training towards building up his Rasengan, we also see how he’s progressed and grown up to become Naruto’s rival.
Naruto Shippuden 421 see’s Naruto and Sasuke talking to Hagoromo, they tell him their desire while he gives them both Indra and Ashura’s Ninshu to allow them go try to defeat Madara before he can attain Kaguya’s power. All while Guy battles against Madara, unable to make a significant dent on him, thus he uses his most powerful technique, Night Guy releasing all his power. He’s about to die when Naruto arrives and saves him.