Another place to check is FanFiction.net. It has been around for a long time and hosts a wide range of fan - created stories, including ones about Yami and Charlotte. However, the quality can vary, so you might need to do some sifting.
One popular 'yami x charlotte fanfic' could be 'A Bond Beyond Worlds'. It explores their relationship in a unique fantasy setting where they have to overcome various challenges together. The story is filled with interesting character interactions and a bit of mystery.
Perhaps a plot where Yami has to pretend to be Charlotte's fiancé for some political reason in the Clover Kingdom. At first, it's just for show, but as they go through the motions of a couple, they start to develop real feelings. They face challenges from the court and other nobles who don't want them together, but they fight for their relationship.
To develop Yami's character, you could explore his past more. Maybe his experiences in his home country before coming to the Clover Kingdom have shaped his views on relationships. And for Charlotte, show her growth from a strict, duty - bound noble to someone who is willing to break the rules for love. You can also use their interactions with other characters in the Black Clover world to highlight their individual traits and how they change in relation to each other.
For Yami, it's important to capture his laid - back yet powerful nature. He has a unique way of speaking, often using casual and sometimes vulgar language. So, in the fanfiction, make sure his dialogue reflects that. Also, show his loyalty to his comrades and his love for a good fight. For Charlotte, her elegance and pride should be prominent. She is a strong mage but also has a soft side that she doesn't often show. Describe her magic in detail to give a sense of her power.
Another fanfiction could focus on their relationship in the context of a magic tournament. Charlotte is determined to show her strength, but she gets into trouble. Yami steps in to help her. This event makes Charlotte realize her feelings for Yami are stronger than she thought. They then start training together, and their relationship blossoms as they learn more about each other's fighting styles and pasts.
One common theme is adventure. Given their abilities and the worlds they come from, many fanfictions send them on exciting quests. For example, they might be on a journey to find a lost magical artifact.
I'm not entirely sure specifically what 'yami x tea fanfic' is about without more context. It could potentially be a fan - made story involving characters named Yami and Tea in a particular fictional universe. Maybe it's a story about their relationship, whether it's a friendship, a romantic relationship, or some kind of adventure they go on together.
In a 'demon yami x yugi fanfic', one aspect could be the way they interact in different settings. Maybe in a battle scenario, Yami's demon powers and Yugi's strategic mind work together in an unexpected way. It could also show their emotional connection, like how Yugi accepts Yami despite his demon side.