Suika is a young girl who lives in the village with the other stone age humans. Her most notable feature is the large watermelon on her head, which she can climb inside to disguise herself as the fruit. Senku first meets Suika when he, Chrome, and Kohaku were searching for iron sand in a nearby river.

Suika is eager to help Senku build his kingdom of science because she's never been useful to anyone before. She comes to work as an information gatherer for the kingdom of science, occasionally being referred to as "Ace Detective Suika."