Just checked first chapter. If he really wanted he could just close his eyes before girls and they wouldn't die.
They wouldn't find his soul mates (one of the conditions to die).
He really wants 100 girlfriends, and at some point they will get pissed... (My guess)...
Edit:
@Lex79 i've just read chapter one... They die just if they met him.
"For those who have met their soulmate..."