In the Demon Slayer manga, Inosuke survives. The story doesn't have his character meet a fatal end. He plays an important role throughout and remains alive at the conclusion.
Nezuko remains alive in the Demon Slayer manga. The author chose to keep her alive as she is an important character with a vital part to play in the overall narrative.
Muichiro's death in the manga occurs during a particularly intense confrontation. His injuries accumulate, and he ultimately succumbs despite his valiant efforts.
Frankenstein, the scientist who created Frankenstein in The Demon Slayer, died in an accident. At the end of the novel, Frankenstein was kidnapped and imprisoned by a group of mysterious people. His body was tortured to a very painful state. Later, Frankenstein's friends, family, and colleagues went to look for him, but in the end, they all returned empty-handed. In the end, Frankenstein died in an accident. His death was described as a tragic death from excessive torture.