The device, developed by printing company Toppan and called VoiceBiz, lets customers speak to a station attendant over microphones while the semi-transparent screen between them spells out their words in Japanese and one of 11 other languages.

More than 2 million visitors arrived in Japan last month, the most since the pandemic kicked off in 2019, and travellers from the United States and Europe exceeded pre-outbreak levels as the weak yen makes the trip the cheapest in decades.

Kevin Khani was among foreign travellers who got turned around in the Seibu-Shinjuku station recently and found the VoiceBiz window helpful.

"The translations were spot on," said the 30-year-old German, who works at Alibaba. "It might sound a bit weird, but you feel safe immediately because you know there's a human on the other side. So you take your time to explain what you need and you will know that they will understand what you need."

Seibu Railway, a unit of the Seibu Holdings conglomerate, installed the translation window this month at its Seibu-Shinjuku station, the terminus of one of its central Tokyo lines, for a three-month trial before considering a wider rollout.

About 135,000 passengers pass through the station daily, including many foreigners shuttling between tourist hot spots, such as Tokyo's new Harry Potter theme park.

"Our goal in introducing this was to improve the smoothness of communication by letting people look at each other's face," said Ayano Yajima, a sales and marketing supervisor at Seibu Railway.

The device was also tested out at Kansai International Airport earlier this year, and Toppan has aims to sell it to businesses and government offices in Japan to contend with both foreign travellers and an ever-growing number of immigrants.

With its many rail lines - some connected, some not - and gigantic bus station, Shinjuku district is the ultimate testing ground for way-finding tech.

Across the road from the Seibu station is Shinjuku's central Japan Railway (JR) station, which is the busiest in the world, with some 3.6 million people passing through daily. A rabbit warren of tunnels connects the JR station to multiple train and subway lines run by other companies.

Weary from a 1 a.m. flight arrival, French tourists Isabelle and Marc Rigaud used the translation window to try to find their way from the Seibu station to the JR station. They still needed a help from a bystander to get there.

"It's very Japan," Isabelle, 47, said.

(Reporting by Tom Bateman and Rocky Swift in Tokyo; Editing by Simon Cameron-Moore)

By Tom Bateman and Rocky Swift