Well, in the light novel, Dazai meets his end. His death is a significant part of the story's development. It has a great impact on other characters as well. His departure leaves a void that can be felt throughout the narrative, and it also changes the dynamics among the remaining characters.
Dazai does indeed meet his end in the light novel. The circumstances surrounding his death add depth and complexity to the narrative, and it has a profound impact on the other characters and the storyline.
In manga chapter 109, Dazai survives. The plot doesn't lead to his death at that point. Maybe there are some intense situations, but he makes it through.
In the light novel, Dazai's fate is not a happy one. His death is a crucial element that shapes the overall tone of the story. It's not a storybook happy ending where he rides off into the sunset. His end is more bittersweet, if you will. It affects the other characters deeply, and the story moves forward with a sense of loss due to his death.