She and her younger sister Fubuki were both born with psychic abilities, but Tatsumaki was the stronger of the two. Unknown to Tatsumaki, her young mastery over her psychic abilities cause the neighborhood kids to be terrified of her, which indirectly led to Fubuki being isolated. At the age of 7, however, Tatsumaki was taken away from her adopted family though her parents were given money for complying by scientists who wanted to study her psychic powers. Tatsumaki was constantly tested on because of her extraordinary abilities, but she was also given toys and candy whenever she cooperated. Lucky for her, the hero Blast came to her rescue and defeated the monster. Afterward, Blast told Tatsumaki not to rely on others to rescue her.
She is recognized as one of the Hero Association's most powerful heroes. She and her sister are known as the Psychic Sisters. Tatsumaki is a petite woman, commonly mistaken for being much younger than she really is. She has an adolescent face with emerald green eyes, and green hair that naturally curls up on the ends. She is occasionally drawn in ONE 's simplistic webcomic style.
From there, the manga launches into a flashback in which a young Tatsumaki is imprisoned at a research facility eighteen years prior. Soon, a synthetic beast breaks free and starts running amok in the facility. The researchers opt to abandon Tatsumaki -- the future number two hero -- because she's not strong enough.