Mikkoku has yet to be released, so there is currently no download link avaiable.
Do you want to help speed up the process of finishing the game? Sign up as a beta tester using this contact form! Any help is more than welcome.
In the meantime, feel free to enjoy yourself with the demo, which can be downloaded by using the following link: http://mikkoku.org/downloads/MikkokuDemo1.0.zip.
Simply extract the zip file and open "Mikkoku.exe" to play the game. If the text is looking ugly, double click on the font "msgothi0.ttc" (included in the zip file) to install it and you should be good to go!