It could be Naruto himself. Since he has a connection to all the villages in some way, he could play a crucial role in the fanfic, perhaps as a mediator or someone who uncovers a hidden conspiracy during the summit.
Perhaps in the fanfic, a young shinobi manages to infiltrate the Five Kage Summit and has a significant impact on the discussions. This shinobi could bring new ideas or warnings that change the course of the kages' decisions. For example, he might have uncovered a plot by a rogue ninja group to take advantage of the kages being gathered in one place. This would not only create tension between the kages and the external threat but also among the kages themselves as they debate how to handle this unexpected situation.
In this fanfiction, Naruto might be pushed to attack the Five Kage Summit due to some misinformation or a threat he perceives to Konoha. Maybe he thinks the Kages are planning something against his village.
It could be a rogue ninja who has a vendetta against all the villages represented at the summit. He might have been wronged in the past by the combined actions of the five great villages and now seeks revenge. He could use the chaos of the summit to launch attacks and try to undermine the stability of the shinobi world.
In a 'naruto five kage summit fanfiction', a great plot could be that the Mizukage reveals she has evidence of a traitor among the other Kages' entourages. This leads to a tense investigation during the summit, with accusations flying and old grudges resurfacing. The story could explore how the Kages balance their trust in their own people and the need to maintain diplomatic relations during such a crisis.
A new, young ninja from a minor village could be the main character. They could be trying to make a name for themselves and their village at the Kage Summit. They might get involved in some political intrigue or even a fight between the Kages and prove their worth.
The fanfiction might explore Dark Naruto's motives during the Kage Summit. He could be on a mission to expose the secrets that the Kages have been hiding from the shinobi world. His actions at the summit could be a way of shaking up the established order. For example, he might reveal a conspiracy among the Kages that has been affecting the balance of power in the ninja villages. This would not only put the Kages in a difficult position but also force the other shinobi present to re - evaluate their loyalty.
In the fanfic, Naruto being cold after the Kage Summit could lead to some interesting character developments. His friends might be worried about him and this could strengthen their bonds. Also, it could be a sign of some sort of new power or curse that he got during the Summit, which would then drive the plot forward as they try to figure out what's wrong with him.
A plot could revolve around a mysterious threat that targets the Kages during the summit. It could be a long - forgotten enemy or a new dark force. The Kages have to put aside their differences and work together to face this threat. They might also discover some secrets about their own villages in the process of fighting this common enemy.