Does anyone know the title of a manga about a girl who is in love with a boy who only dates girls with girlfriends? After the girl breaks up with her boyfriend, he is disinterested and starts to date another girl with a boyfriend?

Thank you!

...only dates girls with girlfriends?... lol sorry I couldn't help myself 😛 .

One that comes to mind for me is Kyou, Koi o Hajimemasu. The guy doesn't exactly pursue girls that are taken, rather he pursues girls that don't like him,

and then leaves them if they start to have feelings for him.

This is completed and has a happy ending too.