It has been revealed that Arashi member Aiba Masaki has been urgently hospitalized due to spontaneous pneumothorax (collapsed lung) in the middle of the night on June 28th.

Spontaneous pneumothorax is when there is air collected in the space around the lungs. This buildup puts a lot of pressure on the lungs and prevents it from expanding normally. This will be Aiba's second time experiencing spontaneous pneumothorax as he was hospitalized with this for 5 days back in 2002.

According to Johnny's Entertainment, Aiba felt sharp chest pains during the filming of "Arashi ni Shiyagare". After the filming ended, he immediately went to the hospital for examination, and was hospitalized. On the 29th, he was diagnosed with spontaneous pneumothorax. Aiba will be hospitalized for about a week, then will briefly rest for his health.

Thanks to Sara for the tip!

Source: Daily Sports Online