Playing in the first group of the day, Joshua Koo of Cerritos, California, jumped out to an early advantage with a 6-under-par 66. Koo carded seven birdies to just one bogey to grab a four-stroke lead entering round two. The 16-year old has two career top-5 finishes in AJGA events entering this week.
In second in the Boys Division is Kai Hirayama of Arcadia, California, at 2-under-par 70. Park and Hirayama are joined in red figures by David Cho of Chino Hills, California, who opened his week with a 1`-under round of 71. Yao Ting Zou of (China) Irvine, California, sits in fourth at even-par 72. Rounding out the top-5 at 1-over-par 73 is Timothy Jung of Corona, California, Ray Xiong of Rancho Santa Fe, California, and Robert Keilch of Newport Beach, California.
Brianna Park of Irvine, California, finished the first round with an even-par 72 to lead the way in the Girls Division by one stroke. Park's round featured four birdies, including one on No. 18, her final hole of the opening round. Park currently ranks No. 244 in the Rolex AJGA Rankings and has five career top-10 AJGA finishes.
Six players are tied for second after 18 holes of play at 1-over-par 73: Angela (Yilin) Liu of Irvine, California; Natalie Vo of San Jose, California; Angela Heo of Murrieta, California; Elina Kuang of Murrieta, California; Lauren Lee of Irvine, California, and Kate Younger of Los Alamitos, California.