I'm not sure about specific 'male Corrin conquest fanfiction' off the top of my head. But you can try searching on fanfiction websites like Archive of Our Own. They usually have a wide variety of fanfictions based on different themes and characters.
One common theme is adventure. Since both Male and Female Corrin are often involved in battles and quests in the game, fanfictions might continue their adventures together, facing new enemies and challenges.
You can also check out some Fire Emblem - related forums. Sometimes fans share their fanfictions there. Just be aware that the quantity might be smaller compared to the big fanfiction platforms.
One popular type might be adventure - themed ones, where the two Corrins go on a quest together. Maybe they are exploring a mysterious new land full of magical creatures and ancient ruins.
A plotline might involve Niles and male Corrin having to go on a quest together. During this journey, they face various challenges that force them to rely on each other and in the process, their relationship deepens into a romantic one. For example, they could be exploring a dangerous, uncharted territory where they have to protect each other from wild beasts or solve complex puzzles to progress. There could also be a plotline where Niles has a secret that he is hesitant to share with male Corrin, but as their relationship grows, he eventually reveals it, which either strengthens or temporarily strains their bond.
You could also try searching on social media platforms like Tumblr. There are many fanfiction writers who post snippets or links to their full works on their blogs. Look for tags related to Corrin and fanfiction. But be aware that the organization might not be as systematic as on dedicated fanfiction websites.
Romance is also a big theme. Writers often explore how they fall in love, maybe starting from initial misunderstandings and then gradually growing closer. Their different backgrounds can create interesting relationship dynamics. Since they come from different fictional settings, there could be cultural clashes and mutual learnings that contribute to their romantic development. This can involve things like Corrin teaching Robin about her world's customs and Robin sharing his knowledge of tactics and magic.
Female Corrin often plays the role of a protagonist or a key character in fanfiction. She might be the one driving the plot forward with her actions and decisions. Azura, on the other hand, can be a supporting character that provides crucial assistance to Corrin. For instance, she could use her singing abilities to soothe or empower in the story.
Often, fanfictions explore the emotional connection between them. Female Corrin might look up to Azura as a source of inspiration. Azura, in turn, could see Corrin as someone with great potential. Their relationship can also be a bit of a mentor - mentee type in some fanfictions, with Azura guiding Corrin in matters of magic or strategy.