Iconic Naruto character Tobirama Senju was among the strongest ninjas in the Hidden Leaf's history, and, prior to the final events of the Fourth Ninja War, in the entire series. A major shinobi who held the office of Hokage, Tobirama is widely appreciated among fans for his pragmatic and blunt personality, as well as his resourcefulness as a fighter.
Considering Tobirama's habit of always keeping his guard up and his exceptional combat prowess, Naruto fans have always wondered how the renowned Second Hokage could lose his life in a battle against Kinkaku and Ginkaku from the Hidden Cloud. This thread will try to shed some light on the subject.
The Second Hokage's death at the hands of Kinkaku and Ginkaku is a controversial event in Naruto
An overview of Tobirama Senju's life
Back in the Warring States Period, Tobirama Senju and his elder brother Hashirama decided to create a new system, so that no child should ever die meaninglessly, as it happened to their younger brothers Kawarama and Itama. After several fights with Madara's Uchiha clan, Hashirama's determination to sacrifice his own life to achieve peace eventually broke through everyone's hearts.
As such, all major shinobi clans, including Senju and Uchiha, reached an agreement to come together, leading to the founding of the Hidden Leaf Village. In the subsequent years, Tobirama acted as the pragmatic voice of reason for Hashirama, who became the Hokage, i.e., the leader of the Hidden Leaf. After Hashirama's death, Tobirama became the Second Hokage.
Guided by a steady faith in the Will of Fire, according to which all the Hidden Leaf's inhabitants were part of a family, he worked to achieve stability. He implemented several institutions, including the Ninja Academy, the Anbu Black Ops, the Chunin Exam. Especially wary of the Uchiha clan, he entrusted them with the Military Police Force, with the aim to involve them and entrust them with responsibility.
Following Hashirama's work, Tobirama also tried to promote good relations and alliances with the other villages. However, during a formal ceremony, he and the Second Raikage were suddenly attacked by Kinkaku and Ginkaku, with the assassination attempt leaving the two leaders on the brink of death.
Sometime later, Tobirama's team, which included the Second Hokage as well as Hiruzen Sarutobi, Danzo Shimura, Kagami Uchiha, Torifu Akimichi, Koharu Utatane, and Homura Mitokado, was tracked down and surrounded by the Kinkaku Force, a group composed of Kinkaku, Ginkaku, and at least eighteen unspecified "elite ninjas".
Notably outnumbered by dangerous foes, there was no way for the Hidden Leaf ninjas to survive a direct battle. Thus, Hiruzen volunteered to act as a decoy to allow everybody else to escape. However, Tobirama didn't allow the young shinobi to risk his life. To everyone's surprise, the Second Hokage himself decided to take his place.
As such, Tobirama passed the title of Hokage to Hiruzen, and went forward against the Kinkaku Force. He sacrificed his life, but his death allowed the others to successfully escape. Considering Tobirama's exceptional prowess, many Naruto fans have always deemed this outcome inconsistent.
A lot of things don't add up in Tobirama's death
Naruto fans have always found it rather disappointing that Tobirama was hopelessly crushed by Kinkaku, Ginkaku, and their allies. The Second Hokage was also backed up by talented ninjas, including Hiruzen Sarutobi, so it seemed odd that he went to die against the same foes that Darui was able to hold his own against.
Although a very skilled fighter in his own right, Darui is not even remotely comparable to Tobirama. Thus, Tobirama's underwhelming portrayal in the issue doesn't make much sense. It must be noted, however, that Darui fought Kinkaku and Ginkaku when they were a bit weaker, as compared to their might in the battle against the Second Hokage.
Distant descendants of the Sage of Six Paths, the two brothers were the most feared criminals in the Hidden Cloud's history. As they ate some of the chakra-imbued flesh of the Nine Tails, they obtained a portion of the mighty Tailed Beast's chakra, which made them sort of pseudo-jinchuriki. This enabled them to use the Nine Tails' power, even entering a V2 form.
Kinkaku and Ginkaku were also especially dangerous, as they could wield the Treasured Tools of the Sage of Six Paths. These items are considered the most powerful ninja tools, and it is said that anyone who uses them inherently obtains might on par or even above that of the typical Kage-level ninja.
During their fight against Darui, the two brothers didn't have the Amber Purifying Pot, the strongest of the five Treasured Tools, which they had available when they assaulted the Second Hokage. Regardless, something still doesn't fit, as, at least on paper - Tobirama had all means to engage Kinkaku, Ginkaku, and the others without dying.
Combining the Flying Thunder God with the Shadow Clone Technique, he could strike the criminals before they could react, even more so as they didn't seem particularly fast characters. However, it must be noted that Tobirama's normal techniques might not have been lethal enough to overcome Kinkaku and Ginkaku's Nine Tails chakra shroud.
In this regard, Tobirama's typical move, which involved summoning corpses with the Impure World Reincarnation to have them explode endlessly with the Mutually Multiplying Explosive Tags, would have been very helpful. Nevertheless, it's possible that he could not have available corpses prepared, which would prevent him from using the technique.
Moreover, the Second Hokage is extremely smart, able to create strategies on the fly. Coupled with his space-time techniques, this should have allowed him to handle Ginkaku and Kinkaku's group much better. Stamina was certainly not a problem, as already back in the day, Tobirama had enough chakra to fight for an entire day against the Uchiha clan.
Being an individual strong enough to beat and kill Izuna Uchiha, whose abilities were comparable to those of Madara before the latter obtained the Eternal Mangekyo Sharingan, Tobirama's crushing defeat at the hands of Ginkaku and Kinkaku's group really seems unaccountable.
Based on what is known of each character, the Second Hokage should have been able to at least hold his own, if not outright win. This inconsistency may be the reason why Naruto author Masashi Kishimoto never showed any scene or additional information about this fight, not even in the series' databooks.
Regardless, dying against Ginkaku, Kinkaku, and twenty other powerful ninjas, after having fought all of them singlehandedly, is not necessarily a bad performance. The enormous disadvantage in numbers is not to be underestimated, as the eighteen unnamed ninjas were all mighty individuals in their own right.
Tobirama himself, who has very high standards, called the eighteen fighters "highly skilled ninjas," which means Naruto fans are not meant to see them as weak opponents. They should have been at least around Asuma Sarutobi's level.
That may not seem so exceptional, but eighteen characters, each one with Asuma's overall strength but different individual skill sets, make a fearsome group. Even mighty S-rank ninjas would struggle in such a situation. Moreover, Kinkaku and Ginkaku were there, with their Nine Tails transformations and Treasured Tools, which are enough to make anyone a Kage-level fighter.
Summing up
Tobirama's self-sacrifice and subsequent death seems a plot hole not only due to its inconsistency with the franchise's power levels, but even more so as it could easily have been avoided. The Second Hokage could just use his Flying Thunder God Technique to escape, instantly teleporting himself and his comrades to the Hidden Leaf, where he certainly must have left a mark.
The are only two potential counter-arguments for this, and neither makes much sense. Tobirama could have wanted to prevent Kinkaku and the others from chasing them in the village so as to not endanger it, but the criminals would not have any means to know that the Second Hokage and his bunch teleported to the Hidden Leaf. Moreover, they could have attacked the village regardless.
The other explanation might be that at the time Tobirama didn't have enough energy left to teleport everyone with the Flying Thunder God. Considering his exceptional stamina as a major member of the Senju clan, this seems rather unlikely.
Unsurprisingly, no further detail about the fight where Tobirama died was ever shown or revealed, almost as if the author himself knew that the event was hardly coherent.