One possible plot could be that Felicity gets a tattoo as a symbol of a new beginning in her life. Maybe she's had a rough break - up or a major life change and the tattoo is her way of reclaiming her identity. For example, she could get a small butterfly on her wrist, representing transformation.
If Felicity has a conservative family, the tattoo might cause some friction. Her parents could be disappointed or angry, thinking it's not proper. This could lead to arguments and a strain in their relationship until they come to understand her reasons.
In some cases, it could be herself. Maybe she pushed herself too hard in her work or training, and her body or mind couldn't take it anymore. This self - inflicted harm could be a key part of the fanfiction's plot, as she then has to deal with the consequences and learn from her over - zealousness.
It could be a way to remember someone important. Perhaps she lost a dear friend or a mentor, and the tattoo is a permanent reminder of them. For instance, if it's a portrait - like tattoo of her master Tsunade, it would show how much she respects and misses her, and how Tsunade has influenced her life and growth as a ninja.
The tattoo could also be a part of a deal she makes in the fanfiction. Suppose she has to make a pact with a powerful being in the feudal era. As a result, she gets a tattoo that binds her to the deal, and throughout the story, she has to figure out how to fulfill the terms of the pact without sacrificing her own values.
Another possibility is that she gets hurt emotionally. Maybe a relationship in the fanfiction turns sour. A betrayal by a close friend or a lover could be considered as a form of 'getting hurt'. This could then lead to her making some different choices in the story and growing as a character from the pain she experiences.
It could be a wizard who is an outcast from the mainstream wizarding society and has made a living by using his magic in unconventional ways, like tattooing. He might have a small, hidden shop where only those in the know can find him.
In the 'harry gets a tattoo fanfiction', he might get a tattoo as part of a bet or a dare. His friends challenge him and, being the brave Harry we know, he accepts. The tattoo could be something really out - of - the - ordinary, like a moving image of his Patronus. This could lead to all sorts of adventures as he tries to hide it from the more conservative members of the wizarding world.
It could be about Ginny's journey to get a tattoo. Maybe she has a specific design in mind that has a deep personal meaning, like a symbol representing her family or a memorable event in her life.
It could be a design of Inuyasha's sword. Since he and Kagome have a deep connection, she might get a tattoo of his sword as a symbol of their relationship and the adventures they've shared together. It would also represent strength and protection, just like the sword itself.