E-Rank Spark? I'm the SSS Dragon God

The son of a corpse cleaner rated Class E, to save his mother who had been cut off from medication, forcefully broke into a trial controlled by a wealthy clan, only to discover an SSS Dragon God sealed within his body, and that all the talents of his enemies were fakes created from serums — he finally staged a comeback, making the young master who had crushed his potion pay the price.