Takeuchi had been amazed at the original 's reception at Udine, and in other overseas territories. "It was beyond anything I had expected," he says. "I had thought of it as a completely domestic film, one that only Japanese people would understand. I'd made it without thinking of the overseas audience at all, but the laughs were bigger abroad than in Japan.

"People in Italy and Brazil were looking at the [Japanese-style bathhouses] and the latest Japanese toilets with the same perspective as [the film's protagonist] Lucius. They were seeing them with the same fresh eyes as this ancient Roman."

Based on a bestselling manga by Mari Yamazaki, the two films have similar storylines: Faced with a new professional challenge, earnest, workaholic hero Lucius Modestus (Hiroshi Abe) slides into a bath to think - and is sucked into a watery time tunnel.

When he surfaces, he thinks he is in the land of "flat-faced slaves". He is in present-day Japan, and the wonders he discovers, including a "washlet" toilet that transports his nether regions into a flowery paradise, set off lightbulbs of inspiration.

Early in his time travels in the first , he encounters Mami (Aya Ueto), an aspiring manga artist whose parents manage a hot springs inn. Entranced by Lucius' classic form (well-exposed since he spends much of his screen time in the near-altogether), as well as impressed by his burning interest in Japanese baths, Mami develops a crush on him and even travels with him back to Rome.

The stories of both films revolve around political intrigue loosely derived from Roman history. In the pacifist emperor Hadrianus (Masachika Ichimura), Lucius' most important client, is threatened by warmongering senators.

One close Hadrianus ally, the womanising general Ceionius (Kazuki Kitamura), is felled by a mysterious illness that Lucius tries to cure with techniques he learned from the "flat-faced slaves". To save the empire, Lucius conceives a plan for a huge hot springs resort that will bring barbarians and Romans together in aquatic bliss.

The paper-thin plot, as expected, serves mainly as a structure for the gags, most of which revolve around Lucius' cultural clashes with the slaves and their marvellous baths. A former male model who has long since proven himself as a serious dramatic actor, Abe plays Lucius with total sincerity - and gets more laughs as a result.

Realising that 's old-is-new theme had international potential after witnessing the audience response at places like Udine for the first film, Takeuchi made the sequel, he says, "feeling I wanted various types of people to see it and enjoy it. So unlike volume I, volume II is made with a foreign audience in mind."

One example of this foreigner-friendly approach involves the sumo wrestlers Lucius encounters in an old-fashioned (but to him new-fangled) public bath, and that he thinks of as round-bellied gladiators who compete with an admirable lack of bloodshed.

These scenes came from the struggles of Takeuchi and co-scriptwriter Hiroshi Hashimoto to differentiate the second film from the first. "We were struggling," Takeuchi says. "We started making volume II in April 2012, and on May 17 I went to see professional sumo in Ryogoku, Tokyo for the first time in my life. It was a big surprise to me - unlike the sumo I'd seen on NHK, it struck me as idyllic.

"People in the box seats were eating yakitori and drinking sake - it was a very relaxed atmosphere. I became really excited, imagining how someone who had been watching cruel battles to the death in ancient Rome would react to such an idyllic scene."

Takeuchi has also tried to appeal to foreign viewers with scenes set in famous Japanese hot springs. The "innovations", including mixed bathing, give Lucius ideas that he uses into his Roman bathhouses, though the thought of men and women soaking together first strikes the strait-laced Hadrianus as simply wrong.

"By presenting images of the great, outstanding hot springs in Japan, we hoped to make viewers interested in experiencing the wonder of Japan's hot springs culture for themselves," Takeuchi says. That goes especially for visitors from Asia who, Takeuchi notes, "have been enjoying [Japanese] hot springs in great numbers, [with] three times as many people from Taiwan, Thailand and elsewhere in Asia coming to Japan for the hot springs now than compared to five or 10 years ago."

More than hot springs travel videos, however, Takeuchi found inspiration in classic Hollywood films set in the ancient world, with William Wyler's 1959 epic being a particular favourite. "Those old films, like , were great in their visual spectacle and scale," Takeuchi enthuses.

In contrast to the first , whose historical scenes were filmed at Rome's Cinecittà Studios on a super-tight schedule, much of was shot on an open set in Bulgaria over a period of weeks, with nearly 5,000 extras filling the film's colosseum. Takeuchi would like to film in Europe again, though he dismisses a as "out of the question - we've done all we can with that story."

"In Europe even ordinary towns make for great images," he says. "You can't shoot images like that in Japan. Also, there's a certain style and feeling to the people here in Italy. They're just natural actors, even when they're living their normal lives."

That nation of thespians will soon have a chance to see in regular cinemas: Tucker Film, a distribution company headed by Far East Film Festival director Sabrina Baracetti, will release an Italian-dubbed version nationwide this month.

"It's like a miracle to me - that this movie with Japanese playing Italians [actually Romans] will be shown in Italy," Takeuchi says. "I'm really curious to see how the Italian audience will react." He adds with a laugh: "And I'm scared as well."