As for now it seems that quite all Johnny's artists are safe. However the houses of some have sustained more or less serious damage. (I'm not certain if the picture above has anything to do with the info below)
It was reported that the houses of Ueda Tatsuya (KAT-TUN), Go Morita (V6) and Yamashita Tomohisa (NewS) are said to be damaged.
As for Yamapi, it seems that he had a car accident, but it was confirmed by his sister that he's safe, "just" his dog is currently at the hospital.
About Ueda Tatsuya was also said that he had a collapse, but he's fine now.
However in the worst case now is probably Hey!Say!JUMP's Hikaru Yaotome, whose house in Sendai was totally finished by the tsunami.
It was now also clarified on Johnny's official website that Aiba Masaki's house hasn't caught fire.
Source boku-kami.jugem