I don't have the exact date of when Jubei was added to Central Fiction off the top of my head. But a good way to find out is to look at the game's patch notes or ask other dedicated players in online gaming communities.
There might be. Given the name, it's possible that someone has created a novel that ties into this concept. However, it's not a widely known mainstream novel.
The 'Onimusha 2 Oyu Love Potion Plus' could be a creative addition to the Onimusha 2 franchise. Maybe it's a new item or storyline that focuses on the idea of a love potion in the context of the game's setting. It might introduce new gameplay elements or character interactions related to the power of this love potion.
Well, Jubei in BlazBlue Central Fiction has distinct features. One of them is his agility. He can move around the battlefield very quickly, which gives him an edge in combat. Also, his special attacks often have a wide range of coverage, allowing him to control the fight to some extent. His design is also quite appealing, with his traditional Japanese look.
Perhaps an old rival of Jubei's who has turned to the dark side. This character would know all of Jubei's weaknesses and fighting styles, making them a formidable foe. They could be plotting to take over the BlazBlue world and see Jubei as the biggest obstacle in their path.
I have no clear knowledge of when Jubei will be released in Central Fiction. Maybe you can search in gaming forums or follow the game's social media accounts to get the latest on this.
Maybe a fanfic where Jubei takes on a young apprentice. This could show his mentoring side and how he imparts his knowledge and skills. You could include scenes of training, as well as the apprentice getting into trouble and Jubei having to rescue them, all while teaching important life lessons.