Michihiro Kono has taken over a company destroyed by the disaster, and is determined to reopen its doors

In less tumultuous times, Michihiro Kono could have expected a seamless transition as the new head of the soy sauce company he took over from his father at the start of the month. But in post-tsunami Japan, Kono is the president of a company that, by any conventional measure, no longer exists.

Yet amid the devastation and despair, Kono's optimism is proof that, just weeks after the disaster that killed 28,000 people, some residents of this fishing town in Iwate prefecture are daring to think of the future.

All that remains of the business his family has run for nine generations is an early-19th-century document confirming its legal status, a handful of metal signs, soya beans and bottles of soy sauce, and an unshakable belief that he will reopen his doors.

"There is no doubt in my mind that we will be back in business," the 37-year-old says. "My family has been making soy sauce in Rikuzentakata since the Edo era, and we owe it to our customers to get back on our feet."

Outside the prefabricated hut that serves as his makeshift office stand crates containing those treasured bottles of soy sauce, including one from a limited edition to mark the firm's bicentenary in 2007. Inside hangs a sign rescued from the debris, bearing one of the company's mottos: spreading gratitude through food.

Yagisawa soy sauce, fermented in barrels made of local cedar, is famed for its exquisite fragrance. Its storehouse was a symbol of the town, which was reduced to rubble by waves that easily breached its 6.5-metre tsunami wall.

At the site of his former factory, a few blocks away from his destroyed home, it is just possible to catch the aroma of soy sauce on the afternoon breeze.

The new plant will have to be built in a different location with a supply of pristine water, he says, and a new generation of clients found if the venture is to survive. It will be at least five years before the next bottle of Yagisawa soy sauce is produced.

Until then, the firm will act as an agent for other manufacturers in an attempt to reconnect with his remaining customers.

The stream of letters urging Kono to rebuild is testament to Yagisawa's place at the heart of Rikuzentakata's commercial life. One, requesting a bottle of soy sauce, was accompanied by a 10,000 yen note and instructions for the change to go towards the firm's renaissance.

"About 70% of our customers died or were made homeless in the tsunami," Kono says. "If we just do the same as before, our sales will be a third of what they were. We need to do a 180-degree turn. This company is 200 years old. If we want it to last another 200 years, this is the moment of reckoning."

The same could be said for the entire town, where 2,000 of the 23,000 residents died and 80% of the 8,000 homes were swept away. Led by a young mayor, Futoshi Toba, whose wife died when waves engulfed their seaside town, Rikuzentakata is emerging as a model for the post-disaster recovery. Earlier this month it became the first town to erect temporary homes, albeit enough for only one in every 50 people who applied to live in them.

The town will need around 4,000 units, but they won't be ready until August. Almost 1,200 people applied to live in the first batch of 36 homes, half of which were reserved for elderly and disabled people, and single women with children. "We're building them as quickly as we can," says Tomoyuki Murakami, a town official.

Authorities in the three worst-hit prefectures have requested 60,000 prefab homes they hope will be completed within six months. But builders are struggling to find space for them on the few slivers of land on higher ground. So far they have secured land for just 8,000 homes.

"There are still about 7,000 people living in evacuation centres in Rikuzentakata, so we want to build more temporary shelters quickly and give people the opportunity to rebuild their lives in privacy," says Murakami, who has continued working despite losing both of his young children in the tsunami. "We're taking slow steps in the right direction."

Yukie Sato, who is living in a school gymnasium with her mother and son, is among those hoping to secure temporary housing.

Her husband, a government official, went straight back to work after being rescued from the roof of the town hall, where he survived by clinging on to the perimeter fence while 70 of his colleagues drowned.

"Even if we get rent-free temporary housing, we will still have to pay electricity and gas bills, and buy food," says Sato, 27. "I don't know how it will all work out. My car was swept away, my workplace has gone, and we have no money."

In Kono's neighbourhood, 99% of which lies in ruins, every child from kindergarten to middle school age was led to safety by quick-thinking teachers and elderly locals, some of whom were swallowed up by waves as they ushered children to higher ground.

But for 24 hours, Kono was convinced that his wife and their three young children had perished. The family were reunited three days later, but Kono's aunt is still missing.

As he waited for news of his family, Kono distracted himself by accounting for his 45 employees and their relatives. It was then he discovered that his head of sales, a 30-year-old volunteer firefighter, had drowned trying to close the harbour gates.

Today he is preparing to attend a welcome party, complete with cups of tea and slices of cake, for two new employees. Before he returns to his makeshift HQ, Kono leads us up a crooked stairway to the temple where he and dozens of others spent the night of the tsunami, shaking with cold and traumatised by the panoramic view of their ruined homes.

"I stood here and thought there's no way my children could have survived." Then, as he gazes at the flattened town below, company president Kono becomes Kono the father, and for the first time today his eyes fill with tears. "It's time to go," he says.

• This article was amended on 18 April 2011. The original said that Kono's grandmother was still missing. This has been corrected.