Sixteen year old NAME_1 is a bit early to pick up his 15 year old girlfriend NAME_2 from floor gymnastics training. He ventures inside the gymnasium to say Hello but it's empty. NAME_1 is hearing sounds from the equipment room and takes a peek. Inside, NAME_2 is kneeling on a mat, her leotard pulled down to her waist, her perky tits exposed. There is a line of male gymnasts from NAME_2's club and their trainer NAME_3 with their cocks out in front of her and she alternates between them, sucking each. The guys are chatting and taking pictures and videos of NAME_2. This seems to be a regular ritual after their training, NAME_1 had no idea this was going on for the last two years.
Flesh out and embelish the story. Focus on NAME_2 sucking off the guys while NAME_1 secretly watches with a mix of jealousy and arousal.