Birthday: April 24
Height: 165 cm
Weight: 46 kg
Chest: 77 cm
Blood type: A
Specialty: Super High-school Level Photographer
VA: Yuu Kobayashi

Koizumi is an optimistic and sensible girl who is generally rather calm. She might come off as a little rude; but in fact, she's a girl that's not afraid to state her mind. She comes off as very confident, but in fact has self esteem issues, comparing her photographs to those of her mother, a famous war photographer. Her mother was away from home most of her life taking pictures out of the country, but her father was a very poor parent, and she had to take over most of the housework, so she has a generally higher expectation of men, but she doesn't dislike them. Koizumi wants to help as many people as she can, however, if you're being impolite, then she won't hesitate to either scold you or let you suffer consequences. Koizumi hates people who lack manners, but it is never said that she hates men. She at first thought of her title of photographer as stupid compared to everyone else's.

She is killed by Peko in Chapter 2, after being hit with a baseball bat in the head.