This is a material I used to show how to write generative adversarial networks to generate MNIST hand-written digit images with KERAS (Ver2) in Shibuya, Tokyo in January, 2019. Source code can be found on Gist (https://gist.github.com/asterisk37n/0875a3d8ec08d81128308b2baaef838a) and it was written as simple as possible without loosing an essence of network.