In many 'HxH Illumi x Reader' stories, the reader has a special power that Illumi wants to use for his own purposes. However, as he spends more time with the reader, his feelings start to change from just using them to actually caring about them. This kind of story often shows the complex character of Illumi as he struggles between his cold - hearted nature and his new - found emotions.
One great 'HxH Illumi x Reader' story could be about the reader being a new hunter and Illumi taking an unexpected interest in them. Maybe he's intrigued by their unique nen ability or their fearless attitude towards the dangerous tasks hunters face.
To develop a fem reader character well, first, give her a distinct personality. For example, she could be curious and adventurous, which would drive her to explore the Sandman world. Second, give her some backstory, like she had a strange dream - related experience in her past that makes her more receptive to the Sandman world now. This makes her more relatable.
The fem reader's character can be developed through her interactions with Pokemon. For example, if she has a difficult time taming a wild Pokemon, but through patience and understanding, she manages to do it, it shows her growth. Another way is by facing challenges in battles. If she loses at first but then learns new strategies and wins later, it's a sign of development.
I don't think so. There haven't been any official announcements or indications that the HxH manga will continue. But you never know, maybe there'll be a surprise in the future.