Think about their dreams and aspirations. Perhaps Mata dreams of becoming a great leader, and Lucas helps him by providing advice and support. You can create scenarios where they exchange ideas, learn from each other, and inspire one another. By focusing on positive character traits and interactions, you can create engaging and respectful fanfiction about them.
You can focus on their friendship. For example, write about how they first met and how their friendship developed over time. Maybe they had to overcome some difficulties together, like facing a common enemy or achieving a common goal.