Episode #18 of the Super Saiyan 4.
This beloved form, first introduced during the GT era, had not been seen for almost 3 decades, and fans had been pleading to see it once again. Yet, the return of Super Saiyan 4 opens the door to a massive plothole, as the transformation was never used during the Super series. Nonetheless, Daima might still have a way to justify this, and it would be an extremely compelling argument.
Super Saiyan 4 Might Need Demonic Magic To Work
The Form Could Be Limited to the Demon Realm
In Dragon Ball DAIMA episode #18, the Z warriors are defeated by Gomah, who is using the Evil Third Eye to reveal his true power. As the imposing villain prepares to destroy them once and for all, the ancient Namekian, Neva, approaches Goku and uses the special ability of his race to awaken a hidden power inside of him. Instead of increasing his base power, as was the case when other Namekians used the ability, the sorcerer's magic gave Goku access to the legendary Super Saiyan 4 form.
The reaction of the fandom was overwhelmingly positive, as followers of the franchise had been waiting almost 30 years to see Kakarot use this ability once again. Nonetheless, the fandom also became concerned, as the reintroduction of this form caused a big issue for the plot of the prequel, Dragon Ball Super. Super Saiyan 4 is far more powerful than any other form Goku had access to after the Majin Buu saga, as proven by his battle against Gomah. Yet, the Saiyan never used it during the Super era, making fans wonder if he could use it.

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Daima appeals to both longtime fans and new viewers alike, but one key question remains—how do Goku’s new adventures fit into the official timeline?
Even though this might seem like a big omission from the series, there might be a reasonable explanation for why Super Saiyan 4 was never introduced in the sequel. Daima’s story primarily takes place in the Demon Realm, an entirely new dimension that does not follow the rules of Universe 7. The most likely reason why Goku gained access to his new form is because of its unique atmosphere and the heavy presence of magical energy in this world. The show could avoid creating any plotholes by explaining that Super Saiyan 4 can only be used inside the Demon Realm.
Dragon Ball Gt’s Lore s This Theory
The Series Had a Similar Explanation for Super Saiyan 4's Origin
When Super Saiyan 4 was introduced to the GT anime, the show explained that Goku and Vegeta had never been able to achieve this form due to a lack of Blutz Waves. It was thanks to this energy source that the Saiyans were able to access their Great Ape form, as they helped unlock their hidden power. Nevertheless, because of the overwhelming power of the Super Saiyan 4 form, Kakarot and Vegeta needed to be infused with artificial waves to gain enough power to transform. Something similar might be occurring in DAIMA at the moment.
Although not regularly brought up in the show, the Demon Realm has been confirmed to emanate a unique kind of dark energy. This could be the new show’s version of the Blutz Waves, a new source of energy needed to awaken the transformation. The constant exposure to Gomah’s magic during the fight could also be the reason why Goku was able to sur his limits and awaken a new power. Regardless, seeing as the original form required a unique type of energy to unlock it, DAIMA may be following a similar formula.
Dragon Ball Super’s Goku No Longer Needs Super Saiyan 4
Kakarot Already Controls the Power of the Gods
The possibility of Daima not addressing the sudden disappearance of Super Saiyan 4, while small, could still occur. However, even if the show never explains this, Goku no longer requires Super Saiyan 4 in Super. One of the first events that take place during the sequel is Kakarot gaining access to godly Ki, making him several times stronger than any other transformation. Even if the Saiyna had access to his legendary form, he would have no use for it, as transformations like Super Saiyan Blue or Ultra Instinct are far stronger than any other.
No matter what explanation Dragon Ball DAIMA decides to go with, the introduction of Super Saiyan 4 will continue to bring fans of the series joy for quite some time. It is one of the franchise’s most iconic elements, and the fact that it is now canon deserves a huge celebration.