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There's two of these I remember. Full Moon wo Sagashite (I think that's the name) and another with like two teenagers that have to hand each other clothes. But neither have a spy theme.
This is indeed most probably Cinderella Boy, starring two people who start sharing a body after a freak accident (and switching back and forth every 12 hours). They eventually come to an agreement and work together as private eyes ; there's indeed a lot of corporate intrigue/espionnage in the series as a whole.
(By an amazing coincidence, the dude's name is Ranma... but the source manga actually predates Ranma 1/2 by a few years.)
thanks it was Cinderella Boy.
it is hard to see in the dark when your eyes are blinded by the light
I don't remember if it was a Gender Bender deal like on Ranma 1/2 but i (barelly)remember the protagonist changed genders at midnight and it was something of a spy series, sorry if i could remember more info i would put it but my memory isn't helping right now.