One of the main themes is the complexity of human nature. Izaya is a character who manipulates others, and through his actions, we see how people can be both good and bad, and how easily they can be influenced. Another theme is the concept of chaos and order in a city like Ikebukuro, where Izaya's actions often stir up trouble and disrupt the normal flow of things.
One common theme could be self - discovery. Since Izaya is a complex character, a female version might also go through a journey of understanding herself.
One popular Izaya Orihara light novel is 'Durarara!!'. It's a great read as it delves deep into the complex character of Izaya. The story is set in Ikebukuro and is filled with various sub - plots and interesting characters that interact with Izaya in different ways, making for a very engaging narrative.
I'm not sure if there is such a specific fanfic. There are countless fanfics out there, and while crossovers between different series like 'Durarara' and 'Harry Potter' are possible, and a character like Izaya Orihara being a fan in that context is a very niche idea. It would be quite difficult to find without extensive searching through various fanfic platforms.
Another theme is self - discovery. The OC often goes through a journey of understanding themselves better while being involved with Izaya. They might learn about their own strength, weakness, or hidden desires. It's like the relationship acts as a catalyst for their personal growth. For instance, in some fanfics, the OC discovers a more assertive side of themselves because of their interactions with Izaya.
One place to look for 'female Izaya Orihara fanfiction' could be Archive of Our Own (AO3). There are often various takes on the character in different stories there.
The complex relationship between Shizuo and Izaya is a major draw. They are polar opposites in many ways, with Shizuo being hot - headed and Izaya being sly and manipulative. This contrast creates a lot of interesting dynamics that fanfiction writers can explore.
Another good place could be FanFiction.net. Although it has a broader range of content quality, there are still some great Heiwajima Shizuo x Orihara Izaya fanfictions there. Browse through the relevant categories or use the search bar to narrow down your search. However, be prepared to sift through a lot of content to find the gems.
There's also 'Izaya and the Unlikely Companion'. In this fanfic, the OC is an artist who gets caught up in Izaya's world. The story is great as it shows how their different worlds collide and how they gradually understand each other more. It has some really well - written dialogue that brings the characters to life.