Looking for a romance manga A girl was hired as a housekeeper or a made or somthing to investigate some rich guy maybe he was a noble anyways its modern times and she went to investigate the guy because her sister is pregnant and she wanted to find out about him but they slowly fall in love but around the end she reveals that her sister is pregnant with his child and he says its impossible. She brings the sister and the sister goes who the heck are you turns out she slept with his cousin or somthing and so happy ending the sister got married to the guy and the those two were happily together as well I just don't remember the title can someone please tell me.

Ooooh, I know I've read this 😐 I promise I'll do my best to try to find it >__<

Haiiro no Cinderella... maybe...

~4400 manga completed
~1700 ongoing...

Yeah I just found it you are correct it was Haiiro no Cinderella though I got some of the details wrong when I posted it must be because I haven't read it for so long.