Pygophilia
Pygophilia is sexual arousal from the buttocks — an erotic fixation on the ass, its shape, feel, and movement. The word joins the Greek 'pygo' (rump) with 'philia' (love). Pygophiles are especially drawn to admiring, touching, kissing, licking, squeezing, or watching the buttocks, and a great ass may be the single feature that most turns them on. It's an extremely common attraction, arguably one of the most mainstream 'fetishes' of all. It overlaps with ass worship, spanking, and anal play. The butt is simply the star of the show.
The buttocks are a powerful visual and tactile draw — their curve, softness, and movement are widely and instinctively arousing — and for a pygophile they're the ultimate focus. Touching, squeezing, and watching them is deeply satisfying in itself.
It plays out as lavishing attention on a partner's behind — caressing, kissing, licking, squeezing, and admiring it, worshipping it, or building sex around positions that showcase it. It naturally leads into spanking, ass worship, or anal play.
Low-risk. If attention extends to the anus, basic hygiene and the usual anal-play caveats apply; otherwise it's simply appreciation. Enjoy.