It was all very polite.

Ambassadors, billionaires, a smattering of Biden family members and even one former president were all in attendance at the fifth state dinner President Biden and Jill Biden, the first lady, have held since taking office.

The gauzy celebration leaned heavily into Japanese fans, cherry blossoms and other tokens of the softer side of the U.S.-Japan relationship. The substance of the state visit of Prime Minister Fumio Kishida was focused on finding ways to counter China, but the style of the dinner was all about highlighting a capital city that owes its springtime resplendence, in large part, to the diplomatic overtures of the Japanese.

As the dinner got underway in the East Room, Mr. Biden toasted “to our alliance, to our friendship.” He kept things similarly light earlier in the evening when he greeted Mr. Kishida at the White House, replying, “Thank you,” to a question from a reporter about expectations that Iran would retaliate against Israel for its strike on an Iranian target in Syria.

Mr. Kishida also leaned into the idea of friendship.

“The Pacific Ocean does not separate Japan and the United States. Rather, it unites us,” Mr. Kishida said during his dinner toast, noting that President Kennedy once said the same thing 60 years ago. “I like this line. I use it so many times that my staff tried to delete it.”

The heavy-handed symbolic gestures were returned by the Bidens. Naomi Biden Neal, the eldest presidential granddaughter who was married at the White House in 2022, arrived in a dress with cherry blossoms printed on it.

Dr. Biden wore a sapphire ombre-effect dress by the designer Oscar de la Renta. Finnegan Biden, another Biden granddaughter, was seated at the head table with her grandparents.

Attendees leaned heavily into pleasantries. Even Rahm Emanuel, the swear-prone ambassador to Japan, was putting his talents toward the art of polite dinner conversation: In an interview, he said he spent some of his visit to Washington helping Paul Simon, the night’s musical guest, figure out how to greet Mr. Kishida in Japanese.

Ashley Biden, the president’s eldest daughter, politely but quickly drifted away from the cameras after telling reporters about her dress. On Tuesday, a Florida woman was sentenced to jail for selling Ms. Biden’s private diary to a right-wing activist group. But outside worries rarely come between a Biden and a state dinner invitation. Ms. Biden’s brother, Hunter, attended a state dinner while under federal investigation last year.

As he entered the festivities against a backdrop of giant painted fans, President Bill Clinton pointed joyfully at a portrait of his wife, Hillary Clinton, the former first lady, former secretary of state and 2016 Democratic presidential candidate. Mrs. Clinton, standing next to her husband in a fuchsia-and-gold caftan, beamed.

“Oh, we’re having a good time tonight,” Mrs. Clinton said to reporters.

The Clintons had been part of a group of attendees invited to the upstairs Yellow Oval Room, where Biden cabinet officials and several diplomatic guests joined in a toast, given in English, by Mr. Kishida, and mingled on the Truman Balcony.

“How pretty is this? This is so pretty!” Gina Raimondo, the commerce secretary, said with a sweeping gesture as she breezed by reporters on her way inside.

At times, the unseemly (compared with cherry blossoms, anyway) business of politics crept in. But several attendees seemed less than excited to talk about Mr. Biden’s re-election campaign — or the issues facing it — when asked. Janet Yellen, the Treasury secretary, ducked a question about inflation on her way into the dinner.

The billionaire Jeff Bezos arrived with his fiancée, Lauren Sánchez, and did not say whether he planned to donate to Mr. Biden’s campaign. Neither did Tim Cook, the chief executive of Apple, when asked the same question.

The actor Robert De Niro, who arrived with his girlfriend, Tiffany Chen, did not answer reporters who asked if he was prepared to campaign for Mr. Biden. Mr. De Niro, 80, was at a recent high-dollar fund-raiser for the Biden campaign in New York City. (He and Ms. Chen are also parents to a 1-year-old — there are worse ways to spend a date night.)

Cecile Richards, the former president of Planned Parenthood, paused to talk with reporters about the importance of spotlighting reproductive rights ahead of the election in November. This week, the Arizona Supreme Court upheld a near-total ban on abortions from the 1800s.

“We’ve made such strides,” Ms. Richards said. “Just to have it all taken away has been very motivating for women and for men.”

Gov. Tony Evers of Wisconsin, a Democrat, also reminded reporters about his state’s significance in November. “It’s going to make a difference between a win and a loss for the president,” Mr. Evers said before heading inside.

Kamala Harris, the vice president, arrived in spangled Valentino alongside Doug Emhoff, the second gentleman. She did not answer a question about Arizona.

As the evening wore on, there were distinct hints that political strategy and not just pleasantries would be on the menu alongside the caramel pistachio cake with matcha ganache, cherry ice cream and a selection of American wines.

Ms. Richards, Mr. De Niro and the Clintons were guests at the head table with the Bidens on Wednesday evening, along with Gov. Roy Cooper of North Carolina, a Democrat who joined a Biden campaign call last week to assail Republican-led abortion restrictions.