As I haven't read this novel, I can't tell you exactly who the main characters are. But if we consider general trends in fantasy novels, there might be a young protagonist on a journey of self - discovery. And when the party splits in volume 2, this protagonist might be forced to choose a side or go on a solo adventure. There could also be an antagonist within the party who has been hiding their true intentions until this point in the story, which then leads to the split.
Since I don't have in - depth knowledge of this novel, I can only speculate. It might be that in the second volume, a new character or event is introduced that creates a rift among the party. For example, a magical artifact is found and some in the party want to use it for good while others see it as a means to gain personal power. This could lead to the split of the party in the story.
The splitting can also be a way to show different aspects of the fictional world. In 'The Dark Tower' series, when the party splits, it exposes different regions and their unique threats and mysteries. Each group may encounter different types of enemies or strange phenomena, which helps to build a more comprehensive and immersive world for the reader.
There is also 'The Lord of the Rings' in a way. While it doesn't have a 'die volume 2', the fellowship does split up during their quest. Frodo and Sam go off on their own to Mordor, while others take different paths to fight the forces of Sauron. It's a classic fantasy novel that features the idea of the party splitting for different purposes in the fight against evil.
Since it's a 'durarara' novel, it might have characters like Mikado Ryuugamine. He is often a central figure in the series. There could also be characters with different backgrounds such as Celty Sturluson, a dullahan. And perhaps other characters who are part of the urban underworld or the regular citizens who get caught up in the chaos and mystery that unfolds in the story. Each character likely has their own goals and relationships that add depth to the overall plot.
I don't know as I haven't read the book. But typically in such fantasy novels, there could be a brave young hero or heroine.
There is also Albedo, who is one of Ainz's loyal subordinates. She is very devoted to him and plays an important role in the story. Her character design is quite interesting, with her angelic appearance but complex personality.
It could potentially have characters like Zoe Washburne. She is a strong and loyal character in the 'Firefly' world, and it would make sense for her to be involved in the events of the unification war. There may also be new characters specific to this volume that we don't know about yet.
I don't know as I'm not familiar with 'Split Screen A Love Story'.
Ainz Ooal Gown is the central figure. He has a very complex personality. He tries to use his knowledge from the game to establish his rule in this new world. Also, there are some of his subordinates like Albedo, who is extremely loyal to him and plays an important role in the story in this volume.
Mikado Ryugamine is one of the main characters. He is a young boy who moves to Ikebukuro.