Sounds bizarre and it is! However, it may be very interesting to analyse his act as an extreme form of sexual behaviour even if it is not directly related to obtaining sexual pleasure. And even if he claims he is an asexual individual.
This case alone is enough to write a whole chapter about sexual psychopathology and hidden sexual motives behind the event!
Please go to the link about genital-cooking Japanese man and read the whole story. Comments are welcome!