Why had Kakashi killed Rin?
Because if the Three-Tails inside her had been released, it would have destroyed the village and harmed its interests.
So,
Obito believed
the events leading to Rin Nohara's death
had all stemmed from the struggle between villages,
and even
from the flaws in human nature.
All of that
was the source of his pain,
and why he remained determined to carry out the Eye of the Moon Plan.
He no longer believed in humanity,
or in villages.
But now,
Aogetsu Hyuga was telling him
that every last bit of it
had been caused by the bastard standing beside him!
Rin's death had had nothing to do with any village.
Madara Uchiha
was the only one to blame!
At that thought,
Obito looked around in anguish.
In that moment,
he understood.
But even with that understanding,
there was nothing
he could undo now.
Still,
there seemed to be
one thing he could do.
Madara Uchiha had already written Obito off entirely and paid him no attention.
Just as Madara was considering how to deal with Aogetsu Hyuga,
Obito suddenly lunged and wrapped his arms around him.
At the same time, he forced his failing eyes open and activated Kamui.
A huge vortex appeared around them.
Madara Uchiha's eyes widened. He twisted his wrist, drove his hand into Obito's chest, and seized his heart.
Obito's face contorted in agony, but he kept his nearly blind eyes wide open, fighting desperately to drag Madara Uchiha into the Kamui Dimension.
Aogetsu Hyuga watched with his hands in his pockets. Obito really did take everything to extremes.
When he was a villain, he had been desperate to destroy the world, arrogantly intent on casting Infinite Tsukuyomi.
Now that he wanted to be a good man, he was desperate to atone.