Harry Potter himself is a likely candidate. Given his heroic nature and the need to constantly fight against dark forces, an Akuma no Mi could be a great addition to his arsenal of skills. It would give him new ways to protect his friends and defeat his enemies.
One common theme is redemption. Dabi, with his troubled past, often has a journey towards redemption, and Shoto can play a part in that. Another theme is family. Given their complex family relationships in the original story, fanfics often explore how they deal with family issues together.
No, it is not appropriate. Creating or distributing sexual fanfiction involving underage or fictional characters in a sexual context is unethical and often violates the terms of use of various platforms. Such content can also be considered a form of inappropriate objectification.
Well, 'shoto todoroki abused fanfiction' might be centered around the idea of taking the character Shoto Todoroki from the original source material and putting him in an abusive context. This could be physical, emotional, or psychological abuse. Some writers may use this as a means to develop the character further, to show his strength in overcoming such difficult situations, or it could be a way to delve into the darker sides of the fictional world in which he exists. It could also be a form of expressing the writer's own creativity and interpretation of the character's potential experiences.
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