Safe Sleeping Drug is a substance used by people who hailed from the New World.
This drug is most likely in the form of a powder-shape substance as it requires for the user to inhale it to take effect on them.
By inhaling some of the relatively safe sleeping drugs, the person who smells it will undergo a trance-like state. Apparently, it makes the user sense their own natural talent, mixed up with something else.
- In the World of 2138, there exists a contrast to the safe sleeping drugs. According to the author Maruyama, in order for Herohero to somehow sleep, he must take sleep-inducing drugs during the process. He noted how Herohero can't successfully sleep without using that drug first.