It could be an unknown enemy who is manipulating Dark Naruto's use of Ino's kunai. This enemy might have a vendetta against the Hidden Leaf and sees Dark Naruto as a tool. They secretly guide him in misusing the kunai to achieve their own evil goals.
In this fanfiction, the plot might revolve around Dark Naruto obtaining Ino's kunai and it becoming a symbol of his new, darker path. He might use the kunai to create chaos among the Hidden Leaf. For example, he could plant the kunai in strategic locations to make it seem like Ino or someone else is causing trouble, thus sowing distrust within the village.
One key element is the creativity behind the kunai replacement. It could be something unique like using a certain type of flower in Ino's case, since she has a connection to plants. Another element is the interaction between Naruto and Ino. Their different personalities and skills come together to make the story interesting. For example, Naruto's impulsiveness and Ino's more calculated approach can create some great conflict and resolution.
Well, there's a fanfic called 'Ino's Ingenious Kunai Substitute'. In this story, Ino comes up with a creative replacement for kunai during a battle when they are running low on supplies. The story delves deep into her character and how she uses her intelligence to overcome the situation. Naruto also plays a crucial role in supporting her plan and they make a great team. It's full of action and some really cool strategic moments.
It could be a rogue ninja who has a deep understanding of the Hiraishin Kunai's power and wants to use it for evil. Maybe he was once a student of Minato but turned bad.
It's hard to say for sure without reading it, but it could be new characters created specifically for this fanfiction set in Ino Kuni.
It could be an unknown ninja who has been secretly studying dark energon for years. He wants to use it to take over the ninja world, believing that the power of dark energon will make him invincible.
It could be a rogue Dark Jedi who has escaped from his own Order and sees the Naruto world as a new place to spread chaos. He might be seeking powerful chakra sources to fuel his Dark Side powers.
It could be Sasuke. If Sasuke continues to pursue his own vendetta in a more extreme way and Naruto's attempts to bring him back fail, Sasuke could become the main antagonist. Their rivalry could turn into a full - blown battle for power and ideology, with Naruto being pushed to his limits and potentially turning dark in the process of trying to stop Sasuke.
It could be a rogue ninja from another village who wants to capture Naruto and Ino for their own gain. Maybe he heard about Naruto's Nine - Tails power and Ino's family's special techniques and plans to sell them to the highest bidder.
It could be Orochimaru. He might be interested in Ino's mind - control abilities and Naruto's Nine - Tails chakra for his own evil experiments. He could try to capture them both and use their powers to create a new type of jutsu or even a new, more powerful being under his control.