Age: 16
Birthday: June 21
Height: 157 cm
Weight: 44 kg
Blood type: A
Hair color: purple

Segawa Izumi is the chairman of her class. She is the younger fraternal twin sister of Kotetsu Segawa. Hayate saved her from an attack from a dog, which stole her doll, when they were young (Volume 17 flashback). She rewarded him with a kiss on his lips in return which got her father worried. They had never mentioned to each other about the incident since they first met in Hakuō Academy as time had blurred their image of each other during childhood.

It is hinted in later chapters that she might have feelings for Hayate.
In season 4, a running gag appeared in which Yukiji started to refer to her and two of her friends, Risa and Miki, as the "Three Idiots."