Power can be determined by many things. In modern society, a person's power is generally directly related to the strength, flashiness, and usefulness of their quirk. People with strength enhancing, transformation, or just all-around 'bright' quirks, quickly rise to the top, while people with less-favorable quirks, or quirks society deems villainous often fall behind into the shadows. So you can understand how low of a level people born without a quirk are considered. Being born quirkless is looked at as a disability. A disease, some have even called it. But this is where they are wrong. Social norms are wrong. Why should anyone be regarded as better than someone else because of a mutation that didn't exist a few years ago? Why should one person be more important than another because of something out of their control? Most importantly, why isn't anyone trying to change it? (The cover art is not mine.)
5 parts