Almost 99% Manga are written in Japan. Why is that so? Do they have any culture which support it? e.g. Naruto, One Piece, Death Note, Fairy Tale, Bleach etc.
Japan makes the world's manga because, manga is, by English-language definitions, Japanese. In reference to manga published in the United States, Wikipedia states:
[T]he original parent loan word, manga, is still used by publishers such as Tokyopop, Harper Collins, and various small presses as a blanket term for all of their bound graphic novels—without reference to origin or location of its creator(s). The significance of the word, however, has mutated outside Japan as a reference to comics originally published in Japan, regardless of style or language. Merriam-Webster's dictionary defines the word manga as meaning "a Japanese comic or graphic novel", reflecting the change of the meaning this word has had once used outside Japan.
Because the word "manga" — being a Japanese loanword in English use – means comics initially published in Japan, there have been attempts to find more appropriate terms for the growing number of publications of manga created by non-Japanese authors. Beside the term “OEL Manga”, there is also the term “manga-influenced comics” (MIC) in use. For example, Megatokyo, which was scheduled to be published by the largest manga producer Kodansha, is still referenced as a "manga-influenced comic". (Emphasis mine)
Manfra is French manga-inspired comics, though, like original English-language "manga", it isn't what fits the common definition of manga used in the United States/in English.
Tl;dr: manga comes from Japan because that is the definition of manga. Western manga-inspired comics are sometimes referred to as manga but don't fit the commonly used definition.