Before moving on, it's worth clarifying a long-standing misconception — the so-called belief that the strongest shinobi in the shinobi world can perform jutsu without hand seals, simply by clapping their hands and shouting a technique's name to make it happen.
In fact, the original manga clearly shows that both Hashirama Senju and Madara Uchiha, when actually performing ninjutsu, still used hand seals.
Although their chakra control was so refined that their seals were reduced to the simplest possible forms, that didn't mean they could omit the process entirely.
For instance, Madara used the "Horse" (午) seal when casting Fire Release: Great Fire Annihilation, and the "Snake" (巳) seal when performing Wood Release, which he wasn't as familiar with. When using Clone Techniques, he even formed the same unique hand seal gesture Naruto used for his Shadow Clone Jutsu.
Hashirama, of course, was no exception.
When Orochimaru first reincarnated him with Edo Tensei, Hashirama made obvious hand seal gestures — even though at that time, his Edo body was an imperfect replica.
Later, when he was resurrected again during the Fourth Great Ninja War, he still used seals: the "Ram" (未) seal for the Four Red Yang Formation, and the "Rat" (子) seal for his Wood Clone Jutsu.
After all, even Indra — the elder son of the Sage of Six Paths — believed hand seals were essential to help refine chakra control. How could later generations be any different?
The only times Hashirama and Madara truly used the "clap your hands and it happens" method were when activating their Kekkei Genkai — their bloodline techniques.
For example, Hashirama's Wood Release, or Madara's Susanoo via his Sharingan, and later, the Rinnegan ocular powers.
Only when activating those bloodline abilities did they no longer require hand seals — much like Sasuke, who never needed to form seals to use his Sharingan's ocular techniques.
As for the famous "hand clap" gesture, that was merely a focus technique — a way to concentrate and refine chakra — and had nothing to do with forming seals.
Even the "strongest tailed beast," the Nine-Tails, performed a similar motion, pressing its two claws together when molding chakra.
...
The next day, Senju Mori officially began preparations to take on disciples.
But before he could accept Tsunade and the others, there were two important matters he needed to take care of.
The first was to formally assume the position of clan head of the Senju — a title that had been left vacant.
Konoha had been founded only twenty years ago, and many of its clans — including the Senju — still retained a strong Warring States Era heritage, where the title of clan head traditionally passed to the strongest member of the clan.
Although Mori was not yet at Tobirama's peak level of strength, he was now, beyond question, the strongest Senju alive since Tobirama's death.
Moreover, at just over twenty years old, Mori was still in his prime, with enormous untapped potential and room for growth.
Since Tobirama's death, the clan elders had lost their greatest protector and influence, while the younger generation already looked up to Mori as their natural leader.
In truth, Mori had effectively been the de facto clan head ever since returning to Konoha — all that remained was the official title.
Even the protocol used by the Hyūga and Nara when greeting him had been that reserved for the Senju Clan Head.
Now that he had ascended to the position of Third Hokage, it was only fitting to settle that final matter of name and title through a formal ceremony.
After two generations of selfless, almost ascetic clan heads — Hashirama and Tobirama — the expectations of the Senju clan members had fallen to rock-bottom levels.
In their eyes, a "good clan head" was now simply someone who was strong, fair in reward and punishment, and at least occasionally willing to listen to his clan's concerns.
Take Tobirama Senju as an example—
even though he never provided any real support to the clan, as long as he didn't excessively harm the Senju's interests, he was still considered a "qualified" clan head.
So, for someone like Senju Mori, it was only natural that not a single clansman would dare oppose him.
On the contrary, the entire clan was overjoyed—ecstatic, even.
Within only a few days of taking office, Mori had already arranged for numerous Senju members to be placed in key positions throughout the village's major departments.
It could even be said that the Senju regained, almost overnight, most of the power and influence they had lost during Tobirama's reign as the Second Hokage.
...
The second matter Mori needed to handle was this:
At the same time that he officially assumed the title of Senju Clan Head, he would hold a formal "Return-to-the-Clan" ceremony for Tsunade.
Although Tsunade was the direct descendant of the First Hokage, Senju Hashirama, all she retained was her personal name, Tsunade, and the honorary title "Lady Tsunade", bestowed by the Land of Fire's daimyō.
What she didn't have was the family name "Senju."
Now, Mori intended to restore that name to her—
to give back to Tsunade a surname steeped in history and honor.
He had already sent envoys to contact Tsunade's parents, who were living in the Fire Capital.
When they learned that another member of the Senju clan had become Hokage—and that this new Hokage wished to bring Tsunade back into the main family—they were overjoyed, utterly and completely willing.
Through this ceremony, Mori sought to show every member of the Senju clan how different he was from the previous clan head, Tobirama.
He was a Hokage who cared about his clan.
He would no longer allow the clan's interests to be sacrificed.
He would protect his kin and ensure that those who truly followed him would live better lives and move toward a brighter future.
At the same time, serving personally as principal of the Ninja Academy and holding such a grand ceremony for Tsunade's reinstatement sent a clear message throughout Konoha:
The "de-clanization policy" promoted by the First and Second Hokage had now been completely abolished—and during the entire "Third Hokage Era," it would never be reinstated.
From this day on, both the great ninja clans and the civilian-born shinobi would be inseparable parts of Konoha, together forming its core strength and unity.
Mori never believed in the extreme idea that one side had to be destroyed for the other to thrive.
Yes, civilian shinobi were a vital part of the village.
But did the clans not also sacrifice and contribute to Konoha's founding?
Was Konoha not originally built by the union of ninja clans?
Civilian shinobi did not need to grow upon the corpses of the clans—
they did not have to feed on the blood and bones of the old clans to prosper.
That kind of thinking was fundamentally wrong.
Anyone who preached such an idea was either an overly naïve idealist or a scheming manipulator with ulterior motives.
Because in such a distorted system, the ones who would truly rise again would not be the multitude of civilian born shinobi—
but rather, the new clans that would inevitably form from them.