Poisons are often featured in Rewrite, be it stemming from familiars or superhumans. Some of the poisons are more relevant to the story per se than others.
Examples of the usage of poison[]
Many characters and creatures in Rewrite can use poison as a weapon. The most notorious of them is Lucia Konohana, since her poison is the thing around which her whole story revolves, but we can also see other examples like Takasago, who has to keep injecting himself with poison in order to make himself stronger after his transformation into a half-familiar.
Familiars who use poisons, either as they attack or after they've been defeated, are also not rare.