Yamauchi had qualifying times in eight different events at NCS, showing her versatility. She also set an all-time Empire best in the 100m breaststroke.
"I wanted to win so bad," Yamauchi said. "I didn't do as well as I'd liked at the nationals in New York. This helps my confidence."
"This gives her a big boost for sure," said Neptunes' coach Dan Greaves. "She practices hard, is a pretty good technician and is always smiling."
Penelope also swam a leg on the third-place 200m medley relay team along with her younger sister, Sophia, and with the Sims sisters, Amanda and Stephanie.
Yamauchi had set an Empire best in the 200m IM in Friday's prelims and then knocked another three seconds off the time in her win.
She and her family moved to Santa Rosa from Napa when she was 11. She then joined the Neptunes. She's looking forward to the Janet Evans meet and the summer nationals in Indiana. Colleges are already showing interest in her swimming skills. She wouldn't mind joining sister Mia at Cal.
Yamauchi won an NCS championship in the 200-yard individual medley, breaking her own Empire record in a time of 2.00.98. She also finished third in the 100 breast and swam a leg on Montgomery's third place 200 medley relay team. Yamauchi swims in regional and national meets with the Santa Rosa Neptunes. She began swimming at age three without lessons when she jumped on a water slide and landed in the pool.