You can start by looking on fanfiction.net. It has a large collection of Fate - related fanfictions, and you're likely to find some good ones about Shirou Kotomine and Saber Alter there. Just use the search function and type in the relevant keywords.
Another interesting one is 'Under the Moonlit Alter'. This story focuses on the more emotional side of their relationship. It shows how their bond develops over time, starting from a place of mutual suspicion to a deep and abiding connection. The author does a great job of describing their internal thoughts and feelings as they navigate their relationship.
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.
Historical fiction doesn't strictly alter history. It rather adds fictional elements or interpretations to real historical contexts. This can make the past more accessible and interesting, but it's not intended to change the factual record.
To alter an image in Manga Studio, start by familiarizing yourself with the toolbar. There are tools for drawing, erasing, and manipulating colors. Also, check out the layer options for more complex edits.