Where did that theory come from? And why do poeple think that?
The first time I saw this theory was when the detective started seeing Mina as Lua. At first I thought it was just the detective projecting his daughter on Mina.
But Luna's ex-fiance mistook Mina as Lua too and now I don't think it's just a coincidence. Maybe I'm wrong and it's just the way both look at him with disdain that is similar but I still think it's a good theory.
I don't think the ex fiance mistook Mina as Lina. It was more like he liked getting looked down upon which reminded him of Lua or something, he is weird and disgusting. And as you said the detective is projecting his daughter on Mina because he was not there for here, which is why he is so overprotective of Mina. But Lua and Mina has nothing in common looks wise and the theory is just so random because we have nothing that indicates that they are sisters. we already know both her mother and father, and she also looks like them.
I feel like the theory that Kang Mina and Lua are sisters is getting stronger...