Looking to advance to the quarter-finals, Hijikata was beaten 6-1 6-4 by American Brandon Nakashima in Houston on Wednesday (Thursday AEDT).
Nakashima, the 2022 ATP Next Gen Finals champion, advanced to the quarter-finals where he will face compatriot Ben Shelton, the top seed.
The 22-year-old Nakashima started the year ranked No.134 in the world, but has climbed to No.87 in the ATP rankings.
Despite Hijikata's loss, there is still plenty of Australian interest in the tournament, with Jordan Thompson, James Duckworth and eighth-seeded Max Purcell yet to play their round-of-16 matches.
Shelton advanced to his first clay-court quarter-final on the ATP Tour with a 3-6 6-4 6-3 win over Zizou Bergs.
"Just really happy to get through it," Shelton said. "It definitely was a long one."
The American is trying not to let the pressure of being the No.1 seed get to him this week.
"I don't really think about it," Shelton said.
"I'm not someone who really checks the draw too much. I just come out here to compete and play."
In an upset, Luciano Darderi ousted second-seeded Francisco Cerundolo 6-4 2-6 7-6 (7-4).
Darderi won his first ATP Tour title at the Cordoba Open in February.Â
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