im looking for this manga where one dark haired dude worked for the army and his mom was a...

im looking for this manga where one dark haired dude worked for the army and his mom was a ballet dancer and he had to catch this mafia dude but i think they knew each other or sum and fell in love and it ended with on jumping out of the train to go to the ballet with him together. the art was stunning and it had only like 5 or 6 chapters i think pllllllss if you know tell me