The duration of the Tekken 8 story mode is not fixed. It depends on how quickly you progress and if you take the time to enjoy all the cutscenes and side quests. Some players might finish it in around 10 hours, while others could spend longer.
Tekken 8 indeed features a story mode. It provides a backdrop and context for the fights, making the game more immersive and giving fans a reason to keep coming back for more.
I don't have the exact number of chapters in Tekken 8's story mode off the top of my head. Maybe try looking at gaming blogs or asking other Tekken players on social media.