Notes: So I just realized that Tobirama was sweating in chapter 620! I know that these are cues for the reader, but damn it, I choose to interpret this as Tobi being legitimately afraid of what Hashi might do. This should not have surprised me, because Hashi is just like Butsuma, but damn, it still did. I wonder how he treated Tobi after Madara's death. Those cannot have been fun times. (Quotes are a mix of Mangastream's and Mangapanda's translations.)
Summary: Hashirama puts Tobirama in his place.
"Tobirama!"
His brother's shout was accompanied by a massive outpour of chakra that cracked the walls around them. Layers of dust were sent flying in a circle that had Hashirama's foot at its centre and pieces of the ceiling crumbled down on top of their heads.
Orochimaru's group was terrified, the youngest of its members hiding for cover. Even those who had remained impassive to Tobirama's earlier threat were now on full alert.
One did not have to look at Hashirama's scowl to realize the murder in his thoughts. That blast had been intended to oppress, to fill the room and push back all other presences in the room. Its imperiousness dominated all others and the promise of violent retribution that it carried was all too easy to discern.
And its recipient was Tobirama.
As the greatest chakra sensor of his time – perhaps of all times – he felt it with triple the intensity of a regular ninja. That wave had simply batted away whatever chakra he had kneaded previously. It was a slap on his senses.
The fact that it was his brother who was the source made it all the worse to bear. Hashirama's was a chakra that he was used to and knew intimately. His system's natural response was to not guard against it. So it was that he felt the blast almost as a physical blow.
"Lower your finger," Hashirama said.
At that moment, Tobirama was certain that his brother would attack him if he did not obey his command. Staring at him now were the eyes of Butsuma, who had never hesitated at breaking one of his children's bones if he saw the need to put them in their place. Staring at him now were the eyes of Madara and of the man who had killed his best friend.
Turning on one's brother was nothing compared to ending the life of a dear friend. Those were the eyes of one who would not flinch at killing Tobirama if it came down to it.
"Fine…" Tobirama replied, feeling the sweat run down his face.
He let his finger rest against his arm once more and let the chakra that he had kneaded disperse naturally. It was humiliating to have to do so openly, in front of everyone, but he had no other choice. In fact, Hashirama's anger had been roused to such an extent that he doubted that the small gesture would be enough to pacify him entirely. Feeling the need to emphasize his position as the submissive follower, he added:
"No need to spike your chakra to those levels… Brother."