Since I haven't read it, I can't say for sure. But it could be a human who has an interest in monster girls and maybe some of the more prominent monster girl characters.
The main character, of course, is often a popular choice. He is the one who has the ability to 'gaze' at the monster girls. Also, the powerful and mysterious dragon - type monster girl can be really interesting to include. Her strength and unique abilities can add a lot of drama to the story.
I'm not sure specifically as the title doesn't give much away. But it could be characters who were involved in the exploration or exploitation of aether. Maybe scientists or adventurers.
It depends on the specific 'dark aether story'. In some versions, there could be a brave hero who dares to enter the dark aether to save his world. Maybe there's also a wise old mentor who has some knowledge about the dark aether.
I'm not sure specifically as the 'dark aether story' isn't a well - defined single story I know of. But it could have characters like a brave explorer who ventures into the realm of the dark aether.
I don't know specifically as I haven't played or read it. But typically, in a love - centered visual novel, there would be two or more main characters who are involved in the romantic relationships. Maybe there's a male and a female lead, or it could be more complex with multiple characters having different roles in the story.
Obviously Naruto would be one of the main characters as the title suggests he is the son of Aether. There might also be characters like Kakashi who could play a role in guiding Naruto through his journey of understanding his connection to Aether.