Chihaya Kisaragi, Vivid Bikini, Idolmaster

The image features Chihaya Kisaragi from The Idolmaster, dressed in her Vivid Bikini costume. She is standing in shallow water with her hands on her hips and wearing a blue bikini top adorned with yellow accents and ruffles. Her long blue hair cascades down to her shoulders, and she sports a bright smile. In the background, other cosplayers are visible, but they are out of focus. The overall atmosphere suggests that this image was taken at an anime convention or cosplay event.