In this fanfiction, Akeno is likely a character who has some sort of relationship with Naruto, either a friend or a love interest, who then does something to break his heart.
Naruto could initially be shocked and hurt. Given his trusting nature, Akeno's betrayal would come as a big blow. He might go into a state of disbelief, trying to figure out why she would do such a thing.
One possible fanfiction could be about Naruto and Akeno meeting in a cross - over universe. Maybe Naruto is on a mission in Akeno's world and they end up teaming up. They could learn from each other's powers and fighting styles. For example, Naruto could show Akeno his Rasengan while Akeno could demonstrate her magic to Naruto.
Their relationship would become more centered around the baby. They would have to communicate more about parenting decisions, like how to train the baby if it has special abilities. Their love would grow deeper as they see a part of each other in their child.
It could be an evil spirit that has possessed Akeno. This spirit might be using her to get to Naruto because it sees Naruto as a threat to its plans, whatever they may be. So the main antagonist would actually be this hidden spirit.
Well, they could have a very protective relationship. Her brother might be overly protective, always looking out for Akeno, especially if she's in a dangerous or tricky situation. For example, if there are some mean characters in their school or community, her brother would step in to defend her.
His presence could also add a lot of emotional depth. Suppose Akeno is going through a tough time, like being bullied. Her brother's reaction, whether it's getting angry and standing up to the bullies or being there to comfort her, can drive the plot in different directions. It could lead to a revenge plot if he decides to take matters into his own hands against the bullies, or it could lead to a more heartwarming story of family support if he just focuses on helping Akeno heal.
A possible plot could revolve around Naruto and Akeno discovering a common enemy. Naruto's experience in fighting powerful foes in his own world would be put to use. Together, they would combine their powers and strategies. Naruto could use his Rasengan while Akeno uses her lightning - based attacks. Their teamwork would be a central focus, and through this, they would strengthen their bond as siblings.
In fanfiction, an Issei - Akeno kiss could signify a deepening of their connection. It could be a way for the author to explore the characters' feelings on a more intimate level. It might also be a plot device to create drama, like if there are other characters who have feelings for either Issei or Akeno and this kiss causes jealousy or conflict.