It proved to be Sun's elite evening in her high school career.
"I said to myself that I wanted to get ahead [in the 200]. You have to believe your body is ready and it's all mental will," said Sun, who guided the Falcons to a fifth-place finish in the team competition with 111 points.
Sun finished second in the 200 last year before rebounding to capture the 500 later that evening.
First-year Crescenta Valley Coach Robert Miller said Sun sets her standards high.
"She knows what to do and gets the job done," Miller said. "You'd have to spin the wheel to find adjectives to describe her."
Sun's first title Friday came in the 200.
She had a two-stride lead midway through the eight-lap race and maintained that margin until the end, where she outtouched Mission Viejo's Chelsey Bruington (1:51.86).
"I didn't know when I would break away and I wasn't thinking about first place," Sun said.
A half hour later, Sun defended her championship in the 20-lap endurance test.
Sun all but sealed her title toward the end, cruising in the final lap to easily beat Mission Viejo's Marybeth Francis (4:56.44).
"It feels just as good to win it again," said Sun, the reigning News-Press Female Athlete of the Year. "I was very nervous when I stepped on the block and I was thinking more about how to swim than the result."
Crescenta Valley freshman Yumi So gave the Falcons two impressive performances. She took second in the 200 individual medley (2:06.35) and third in the 100 butterfly (56.39).
Sun teamed with Michelle Du, Minah Kim and So to take sixth in the 200 medley relay (1:51.97), and the quartet placed 11th in the 200 freestyle relay (1:41.12).
Crescenta Valley boys' athlete James Martin, who will attend USC in the fall, turned in two respectable marks.
Martin was third in the 100 backstroke with a season-best time of 52.09, and he posted a season-best mark of 58.74 to place fourth in the 100 breaststroke.