Email?

[lousith]

is there any manga/comic artist who reply if you email or send them a letter ?

[Alex L]

If you can email them in Japanese? Possibly... though doubtful.

Chances are you'd have to send a letter to their publishing house, who would then pass it on to the artist in question. Not too different than stateside. :)

On top of that, there generally is no one artist for a manga. It's a team who draws it all -- based on the character designs from one person, I'm sure, but a single artist does not fill the weekly page quota.