Perhaps Godzilla in human form falls in love with a human. But he is constantly worried about endangering the person he loves because of his true nature. He has to battle his own kind, who see his relationship with a human as a betrayal, while also trying to keep his human love interest safe from the chaos of the kaiju world.
One idea could be that Godzilla, as a human, has to hide his true identity while trying to understand human emotions. He might struggle with the concept of love and friendship, which are very different from his previous existence.
One idea could be a human scientist who discovers a way to communicate with Mothra and tries to convince her to team up with Godzilla against a new common enemy, like an alien invasion. The scientist could be in a race against time as the world is being quickly overrun.
One idea could be a story where the Bakugan in human form have to blend into human society while hiding their true identities. They could face challenges like going to school or getting a job without revealing their Bakugan nature.
Another plot could be that Kurama's human form has a special ability that is unique even among his demon abilities. This ability attracts the attention of both good and evil forces, and he has to figure out how to use it without causing chaos.
One idea could be that the Kyuubi in human form becomes Naruto's mentor in secret. He teaches Naruto some ancient and powerful jutsu that were lost over time. This could give Naruto an edge in battles and also deepen his connection with the Kyuubi.
One idea could be that the Godzilla sees the human child in a dangerous situation, like a collapsing building during a battle, and decides to protect the child. It could then form an unlikely bond with the child, who is not afraid but rather curious about the giant creature.
One plot idea could be Amaterasu living among humans in her human form and using her divine powers secretly to help them. For example, she might use her ability to control nature to end a drought in a small village. Another could be her forming a friendship with a human artist who, unknowingly, starts to paint pictures that are prophetic due to her influence. A third idea is that she has to hide her identity from a group of hunters who are searching for any signs of the divine, as they believe the gods are causing chaos.
One plot idea could be Naruto gradually learning to fully control the Kyuubi's power in a more conscious way. He could discover new abilities that are a blend of his own ninja skills and the Kyuubi's raw power. For example, he might be able to use the Kyuubi's chakra to create illusions that are more powerful and realistic than normal genjutsu.
A really interesting plot could be Acnologia in human form forming an unlikely alliance with the Fairy Tail guild. He could be on a quest to redeem himself for his past dragon - related atrocities and the guild helps him in some way. This could lead to many adventures where he has to use his human skills and not just his dragon powers.
A fanfiction could explore the idea of Shin Godzilla having a more sentient side. Maybe it tries to communicate with humans through some form of telepathy. The story could then revolve around the humans trying to understand what Godzilla is trying to say and if they can co - exist. For example, Godzilla might be warning about an upcoming natural disaster that only it can sense due to its connection with the earth.