I'm not sure who 'Toshiko Kasen' specifically is in Liberty City Stories. It might be a relatively unknown or a character specific to certain aspects of the game that not much information is readily available about.
I don't really know the significance of Toshiko Kasen in the game as there's not much information provided. Maybe she's just a minor character with no major significance.
Since there's no common knowledge about Kazuki Kasen in relation to Liberty City Stories, it could be that Kazuki Kasen has no real significance in the official game. However, if it's a personal or fan - created concept, Kazuki Kasen might be a character that represents a new perspective or story within the Liberty City setting.
I'm not entirely sure who 'Kazuki Kasen' is in relation to 'Liberty City Stories'. 'Liberty City Stories' is a game in the Grand Theft Auto series. It features a fictional city filled with various characters and storylines. Maybe Kazuki Kasen is a character created within a fan - made context related to this game.
The Jujutsu Kaisen manga is indeed ending. It's been a great run, but all good things must come to an end. The final chapters are bringing closure to the characters and story arcs.