The family and friends of a US Navy officer jailed in Japan hope that President Joe Biden's trip to the nation for the G7 summit will yield progress in his case, particularly after he penned a handwritten letter to his wife expressing despair about his situation.

"I'm not doing that good," Lt. Ridge Alkonis wrote in a letter dated April 30, which was shared with CNN. "The walls and bars seem to be making my cell even smaller as of late."

"I feel closer to an animal than a human being now," Ridge Alkonis wrote.

"That was the most dejected I've ever heard him," his wife, Brittany Alkonis, told CNN on Thursday.

Ridge Alkonis, who was stationed in Japan, was sentenced to three years in a Japanese prison in October 2021 for negligent driving resulting in the death of two people and injuries to a third person in May 2021. He said he suffered from acute mountain sickness as he was driving with his family from Mount Fuji, which caused him to lose consciousness. That argument was rejected by the court. His appeal was denied in July 2022.

"Prison has always been a hard place. You know, he talks about how just anything that would bring you happiness is not allowed. He says it's just soul crushing," Brittany Alkonis told CNN.

The Alkonis family claims that there have been violations of the status of forces agreement between the United States and Japan during the proceedings of the case, and they note that they offered to pay a cash settlement to the families of the victims so that Ridge Alkonis could avoid jail time.

Now, they are pushing for him to be transferred back to the US under the Council of Europe (COE) Convention on the Transfer of Sentenced Persons, which would allow him to serve out his sentence there.

Under the terms of the treaty, which Japan joined in 2003, "The prisoner, the Government of Japan and the U.S. government must all agree to the transfer," according to the US Embassy in Japan. "Transfers can take 2 years or longer from the time the process begins," it notes.

She said that parts of the US government have been "incredibly proactive" on that request and in pushing for a resolution to her husband's case but claimed that the US Department of Defense as well as the Japanese government had not productively engaged. He has not been designated as wrongfully detained by the US State Department.

As such, despite her hope for positive movement coming out the G7 trip to Hirsoshima, Brittany Alkonis said she does not have high expectations of a resolution.

Biden raised the Alkonis case with Japanese Prime Minister Fumio Kishida during his visit to the White House in January, and after that meeting the US and Japan agreed to setup a working group to "try to solve this problem," Brittany Alkonis said.

Shortly after that Brittany Alkonis briefly interacted with Biden earlier this year in a chance encounter when she attended the State of the Union address as a guest of Arkansas Republican Rep. Bruce Westerman.

Asked by CNN if the president raised it in his meeting with Kishida in Hiroshima Thursday, a White House spokesperson said they had nothing to add to the public White House readout, which makes no mention of Alkonis. The spokesperson added that senior officials have consistently raised the case with their Japanese counterparts in an effort to achieve a resolution.

The Japanese Embassy in Washington declined to comment on the case.

Brittany Alkonis said that US administration officials have described the working group as having "fallen flat," with the Japanese "starting to ask the same questions that have already been asked and answered."

"The president raising this issue, the ambassador raising this issue, you know, that has made it very clear that this is important to the US and they are an ally and they understand that when something matters to the President, and he brings it up that it's a big deal. But based on Japan's response, it doesn't seem that they do think it's a big deal," Brittany Alkonis said. "So what is raising it again going to do?"

Brittany Alkonis and her children have been able to visit Ridge Alkonis every few weeks in prison, with the current setup allowing for five half hour visits per month, she said. Her children -- all under the age of ten years old -- are the ones who "are paying the price" for this challenging situation between two allies, she said.