Sony launched Xperia Z4 in Japan just two months back; in April. Although, Sony equipped it with nice hardware and gave it decent specs like Qualcomm Snapdragon 810 chip set, just within two months complaints about over heating started pouring in from the Japanese users.
The users have given vent to their feelings on the media and express their opinion on Twitter telling about the over heating problem on the smartphone and later this opinion was supported by the results shown about CPU-Z that the Xperia Z4 gets really a little hot. To make the users aware about this fact Japanese carrier NTT DOCOMO adopted the practical approach and placed some cautionary sings in their outlets so that users can note it and decide accordingly.