the president of the Chemistry club at Rentarō's high school, and specialises in creating drugs that have strange effects when consumed. She is eighteen years old, but due to having consumed a drug that was supposed to make her immortal, she spends much of her time in an eight-year-old body. She also has a neutralization drug that can revert most of her drug's effects. However, the effects of the failed immortal drug can only be temporarily negated, allowing Kusuri to appear in her true 18-year-