Sakura also often appears. She might be confused by the changed behavior of the reincarnated Sasuke. Maybe the reincarnated Sasuke is more open and friendly towards her than the original Sasuke, which would lead to different interactions between them.
One interesting plot point could be the protagonist using their prior knowledge to change certain events in Sasuke's life. For example, they might try to prevent Sasuke from leaving the village earlier than he did in the original story.
Well, of course, the main character who is reincarnated as a kaiju. There are often scientists or military personnel who are trying to deal with the appearance of the kaiju. Some fanfictions might also have other kaiju as characters, either as friends or foes to the reincarnated kaiju.
The protagonist is of course a common character. Usually, they are someone who has a deep love for games in their previous life. There are also often mentors or guides in these stories. They could be an old wizard or a powerful knight who helps the protagonist understand the new world.
The most common character is obviously the tree itself. Then there are often animals like birds, squirrels, or deer that interact with the tree. Sometimes, there might be a forest spirit or a dryad that has a special connection to the tree. There could also be humans, such as a woodcutter or a wandering traveler who stumbles upon the tree.
Well, of course, Goku is a very common character. Since the story is about being reincarnated as a Saiyan, Goku's presence is often there either as a mentor or as a benchmark for the main character's power level.
In addition to the obvious ones like Naruto and Sakura, other characters from Sasuke's clan might interact with him. For instance, if there are any remaining Uchiha members, they might have mixed reactions. Some could be shocked and try to figure out what happened, while others might be more accepting. Also, characters like Shikamaru, who is very observant, would surely notice the change in Sasuke and might have some unique interactions, perhaps trying to figure out how this change could affect their team dynamics or the overall situation in the village.
Batman is quite popular. Reincarnating as him gives the character a chance to have all his gadgets and detective skills. Also, Superman is a common choice. Having his superpowers and being able to fly around Metropolis would be exciting. Wonder Woman is another one. Her connection to the Amazonian culture and her superhuman abilities make for great fanfiction material.
Naruto is often paired with Sasuke. Their bond is so strong that in post - war fanfictions, they are usually shown working together to rebuild the shinobi world. Sakura is also a common character paired with Sasuke. Since she has feelings for him, in these fanfictions, she might be trying to get closer to him and help him heal from his past traumas.
The other Z - fighters like Gohan, Piccolo, and Krillin are also common. Gohan could be a friend and training partner to the reincarnated character. Piccolo might be a bit more reserved but still offer his wisdom, and Krillin could be the one who provides some comic relief in the story while also being a reliable ally in battles.
Cheelai and Lemo from the Broly movie might also be paired with the reincarnated Broly. They could act as his guides or friends in the new world he finds himself in, helping him navigate the complex politics and power dynamics of the Dragon Ball universe.