Momiji Nishiya of Japan takes gold in the street skateboarding competition.

Skateboarding is making its Olympic debut at these Games, and Monday was the close of the street discipline, which was contested on a playground of stairs, rails and short ramps meant to simulate something like a schoolyard or an office park. Athletes performed two 45-second runs and five single tricks, and each was judged on a 10-point scale. The four best scores were added together.

There may be an even bigger infusion of youth next week, when skateboarding’s park competition is held with athletes skating in a concrete bowl. In the women’s division, the youngest athletes all have reasonable expectations to win medals.

Kokona Hiraki of Japan is 12 (she will turn 13 a few weeks after the Olympics), but two bigger favorites are Sky Brown of Britain, 13, and Misugu Okamoto of Japan, 15.

The generational shifts were already on full display in street, however, as teenage girls elbowed away the skaters they had long looked to for inspiration.

None may be more of a role model than Bufoni, 28, one of the most famous skaters in the world, who won her sixth X Games gold medal this month in California. She needed a big score on the final trick of her preliminary heat. She landed the trick, but the score fell short of what she needed to reach the final.

She was upbeat afterward, showing little of the heartbreak that consumed her friend Nyjah Huston the day before. Unlike Huston, she said, she does not win nearly every contest, so she knows that losing is part of the deal.

Bufoni spent the finals in the grandstand, empty of fans, rooting for Leal. The two spent most of the past few months together, and Bufoni wanted to give her some pre-final advice: Have fun. You are too young to have pressure.

Leal skated with exuberance, punctuating her runs and tricks with big smiles. Her biggest problem was that she was not alone in skateboarding’s rush to youth.