Concentration line background is a vector of shirokuronekoya author. This vector includes Concentration line, radiation, Effect line, wallpaper, flashy tags. To download vector (JPG, SVG, PNG, AI/EPS types) you need to register the account and log in.
As the free account, you can download for free with some limits.
As the premium account, you can download unlimited, no waiting time, etc. Enjoin premium membership at here