Aozora Meikyuu had Steam trading card support added on February 16, 2016. There are 5 cards in the series, and you'll receive 3 cards at random for purchasing and playing the game.
Aozora Meikyuu Sora at the Labyrinth
Aozora Meikyuu Sora Selfie
Aozora Meikyuu Sora with Ponytail