我查了质料，那就是日本天团，“安全地带”在1980年代发行的歌曲“Friend （情书) ”。
For those who are catching Friendly Fire, you may want to know what is the title of the Japanese song.
The answer is "Friend", sung by Japanese rock band, Anzen Chitai.
Anzen Chitai front many songs that were chosen to be sung in Cantonese by many of the Cantopop stars.
And the choice of songs seems to be the one positive aspect of TVB dramas. From 2012's Ghetto Justice 2 using Adele's Someone Like You and Rolling In The Deep, who will not forget the The File of Justice series from 1992 to 1997? When the producers chose the right English pop songs to make lawyers in the drama so hip and trendy.
I chose the above MV to showcase the original 1980s version of the song Friend. If you want to know what the song is about, you can approach your Japanese friends or people who know Japanese language for help.