Giyu survives in the manga. The plot doesn't lead to his death. His character has many adventures and developments that keep him alive and active in the story.
There was no clear connection between Sanguine Red's novels," Tengen " and " Tengen 1 ", which could form an independent series. However, judging from the name, Tengen could be considered a follow-up to Tengen 1 because Tengen was usually used to refer to the first work in the series. However, this was not absolute, because the name connection did not necessarily mean that there was a direct causality between the works.