Tuesday’s match came 713 days after Raducanu’s last appearance on grass, having had wrist and ankle surgeries in 2023 that ruled her out of Wimbledon.
Playing at the venue of her very first WTA match in 2021, months before her astounding run to the US Open title, Raducanu showed her intent early on by breaking Shibahara in the opening game.
Shibahara, predominantly a doubles player who won the French Open mixed title in 2022, was playing her first singles match on grass at Tour level but proved no match for Raducanu in the early stages.
After saving two break points, the British number six went on a run of seven successive games to see out the first set and continue into the second, halted only by a Shibahara hold to love.
But, after going a double break up with a 5-1 lead, cracks started to appear in Raducanu’s performance as calls went against her.
Serving for the match, she conceded a break for the first time, before Shibahara then held to love for a second time.
At the third time of asking, the Japanese player broke again to wipe out Raducanu’s second-set advantage.
But that was where Shibahara’s resurgence ended as Raducanu sealed her place in the second round, converting her first match point on her opponent’s serve.
She will face Daria Snigur next after the Ukrainian defeated compatriot and second seed Marta Kostyuk 6-3 6-3.
“It’s been quite a few weeks since I last played a competitive match so I didn’t really know how it would go,” said Raducanu.
“I think my intentions were great from the start.”
Later, Britain’s Fran Jones followed Raducanu into the second round with a 7-6 (7-3) 6-3 win over eighth seed Caroline Dolehide of the United States.
Jones will face another American, Ashlyn Krueger, next.
Women’s top seed and world number 10 Ons Jabeur of Tunisia beat Colombia’s Camila Osorio 6-2 6-3 and will face Czech qualifier Linda Fruhvirtova in the second round.