I am sure all the music parts were rehearsed. Midori was naming her guitar influences and then played a riff from that particular guitar player's band. The long curly haired white guy is the famous Marty Friedman, the lead guitarist of Megadeth from 1990 to 2000. He has lived in Japan since 2003 which is why he learned the language.
The white guy is Marty Friedman from megadeth and as for the picture of LOVEBITES without Miho this interview was after she left the band and before Fami joined