I tried looking and the only one that made sense to me was the rose of Sharon, since it's native to Korea and symbolises eternity, but it doesn't really look like the drawing, so idk
I was checking and I think it's a purple petunia. In flower language it means: Enchantment, Fantasy, Charm, Grace, Mystery. Also it means being with you is soothing.
The one that looks closer is a petunia
So I did an image search and apparently it's called balloon flower and in Korean culture it represents eternal love
Been trying to search but couldn't find it