I'm not sure specifically what 'jeane the cat visual novel' is about as it could be a relatively unknown or niche title. It might be about the adventures of a cat named Jeane. Maybe it follows her daily life in a fictional world, her interactions with other characters, or perhaps she has some special quests or challenges to overcome.
Since I'm not familiar with the 'Jeane Cleaning House Novel', it could potentially revolve around the concept of house - cleaning from Jeane's perspective. It might describe how she tackles different cleaning tasks, her feelings towards the house she is cleaning, and any challenges or surprises that come her way. For example, she could find an old family heirloom while cleaning under a dusty bed, which then sets off a series of events related to the history of the house and its former inhabitants.
I don't know for sure who the main characters are in 'jeane the cat visual novel' since I haven't read it. But it's likely that Jeane the cat is one of the main characters. There might also be other animals or people that Jeane interacts with, like her owner if she has one, or maybe some friendly mice or birds in her neighborhood.
There are often masters who play important roles. For example, Shirou Emiya can be one of the key characters in the Fate - related stories. He has his own goals and ideals which interact with Saber Alter's story.
There might be some out there. You could start by checking fanfiction websites like Archive of Our Own or FanFiction.net. Just search for those specific names and see what pops up.
One common theme could be friendship. The characters might form unique bonds within the circus setting. Another could be mystery, as the 'lamia' aspect might bring in some elements of the unknown.
An alter ego is definitely a fictional character. It can be a way for an author or creator to explore different traits, emotions, or situations that the main character might not be able to express directly. It's a common literary device used to spice up the narrative.