Seiichiro Nishimoto, CEO of Shelter Co., poses wearing a gas mask at a model room for the company?s nuclear shelters in the basement of his house in Osaka, Japan April 26, 2017. REUTERS/Kim Kyung-Hoon

The house of Seiichiro Nishimoto, president of the Shelter Co., where the model room for the company?s nuclear shelters is installed, is pictured in Osaka, Japan April 26, 2017.

Seiichiro Nishimoto, CEO of Shelter Co., poses wearing a gas mask at a model room for the company?s nuclear shelters in the basement of his house in Osaka, Japan April 26, 2017.

Seiichiro Nishimoto, CEO of Shelter Co., poses in front of a blast door at the entrance of a model room for his company?s nuclear shelters during an interview with Reuters in Osaka, Japan April 26, 2017.

Seiichiro Nishimoto, CEO of Shelter Co., poses wearing a gas mask at a model room for the company?s nuclear shelters in the basement of his house in Osaka, Japan April 26, 2017.

Radiation-blocking air purifiers are seen in the model room of Shelter Co.'s nuclear shelter in the basement of its CEO Seiichiro Nishimoto's house in Osaka, Japan April 26, 2017.

Radiation-blocking air purifiers are seen in the model room of Shelter Co.'s nuclear shelter in the basement of its CEO Seiichiro Nishimoto's house in Osaka, Japan April 26, 2017. Image for illustrative purpose.

Emergency foods are seen in the model room of Shelter Co.'s nuclear shelter in the basement of its CEO Seiichiro Nishimoto's house in Osaka, Japan April 26, 2017.

The entrance of Shelter Co.'s nuclear shelter model room, which is placed in the basement of the company's CEO Seiichiro Nishimoto's house, is pictured in Osaka, Japan April 26, 2017.

Seiichiro Nishimoto, CEO of Shelter Co., demonstrates how to use a radiation-blocking air purifier in case of power outage at the model room for Shelter Co.'s nuclear shelters in the basement of his house in Osaka, Japan April 26, 2017.

A gas mask, a Geiger counter and emergency goods are seen in Shelter Co.'s nuclear shelter model room in Osaka, Japan April 26, 2017.

The exit of Shelter Co.'s nuclear shelter model room is pictured in the basement of its CEO Seiichiro Nishimoto's house in Osaka, Japan April 26, 2017.

A blast door is seen at the entrance of Shelter Co.'s nuclear shelter model room, placed in the basement of its CEO Seiichiro Nishimoto's house in Osaka, Japan April 26, 2017. REUTERS/Kim Kyung-Hoon - RTS13Z30