It's a Free Reversi Game. You play with Cute Chicks. ("Piyo" is chick twitter.)
It's Cute, but with high functionality, AI is also authentic.

【Game Function】
・Level of AI is 20 stage, enjoy from beginner to advanced!
・It is possible to play against not only [Player vs AI] but also [Player vs Player]. (It's not a network)
・Marks are displayed in places where chicks can be placed, easy for beginners
・"Hint" button will tell you the recommended move.

【Analysis Function】
・Equipped with game record analysis function.
　It is a function to analyze all moves, find bad hands, and evaluate
・Displays the results of the game analysis on a graph.
　You can see at a glance which move was bad.
・You can copy and paste the game record to the clipboard and link with other apps.

【Official Website】
Please refer to the following for details about this application.
http://www.studiok-i.net/ios/hiyoko_rev.html