zenitsu going crazy

Hard to say for sure. It would depend on various factors like the story's setting, the characters' actions, and the overall tone of the manhwa.

No, Zenitsu doesn't die in the manga.

No, Zenitsu doesn't die in the manga. His character survives through the story.

No, Zenitsu doesn't die in the manga.

No, Zenitsu doesn't die in the manga. He survives through the various story arcs.

One common theme is self - discovery. Since Zenitsu has a complex personality, many fanfics focus on him finding out more about himself, his powers, and his place in the world. Another theme is friendship. He often forms strong bonds with other characters in fanfics, like Tanjiro and Inosuke.

No, Nezuko doesn't marry Zenitsu in the manga.

It's hard to say exactly. The contents of Zenitsu's letter could vary depending on the context and plot of the manga at that point.

Zenitsu doesn't die in the manga. His fate remains alive throughout the story.

Definitely not. In the manga, there's no such plotline of Zenitsu and Nezuko getting married. Their relationship is more focused on being comrades in the fight against demons rather than a romantic one leading to marriage.