We do not know what a KIKIYAMA is. It is speculated that it is either Madotsuki or a person who just happens to be a game designer unusually good at weird scenario writing.
KIKIYAMA is also the creator of Yume Nikki.
For a very long time, it was thought to the English community that Kikiyama had no form of contact, as his/her website hasn't been updated, and the only mention of him/her in public was an interview on a Japanese website (unconfirmed). However, a recent thread on Uboachan revealed that all this time, his/her email address was available. A member contacted him/her and asked him/her whether or not he would update the game, and it was confirmed that Yume Nikki would make it past version 0.10, albeit very slowly.
Recently, a link was posted on Uboachan to a MySound profile and Pokebis thinks it's KIKIYAMA. Link here.
It seems like the account doesnt exist anymore, as the host site went down a few years back. It can be accessed in part using the Wayback Machine (http://waybackmachine.org/).