Etc: Tetsu has also made Ai to Yuuki to Kashiwamochi and Maou Monogatari Monogatari, both of which star girls.
Irisu Syndrome is one of the most unique puzzle games I have ever played. Not just in gameplay but it every aspect of it's execution. From the story being introduced bit by bit every time you lose, to finding out the backstory behind the game's events through hidden text files that appear on your computer when you reach certain milestones.
Irisu herself starts out like some kind of cute bunny-girl witch mascot character to draw you into the game - which would not be at all unusual, especially in the somewhat story-sparse puzzle genre. Instead, the game you play is Irisu's thinking process, and success or failure at such directly determines what she will do - a most intense form of action vs consequence.
The game is best described as psychological horror, and 'success' is not easy. While Irisu may seem to settle into a sort of stereotype, I think the use of the player's skill adds a nice depth. And the game has no shortage of twists to keep you thinking as well.