OHRITE. =D En la wiki pusieron información de sus vidas pasadas (te digo sólo por el squee del personaje, que la dorkeza de Murata me tuvo en capslock hace unas noches):
It was established in a drama cd that he Placed 2nd in the country on the trial entrance exam to the University of Tokyo. Also, even though hes still a high school student hes developing software and trading stocks.
In Murata Ken's last life before this one he was an adult film actress named Christine who lived in Hong Kong. And the life before that he was a French doctor named Henry Régent, He appears in the extra story novel "Ojyousama to wa Kari no Sugata!" His other lives include a Spanish bread maker, a Venetian bakery worker, an ancient Egyptian mummy maker, and a knight in the crusades.