Being friends since childhood and also being in the same affiliation, Shizuru looks up to Lucia like an older sister. She is also useful when when it comes to keeping Lucia in check due to her violent temper tantrums. Shizuru has high resistance to Lucia's poison which enabled them to become friends. She said herself that when Lucia is upset she allows her to cry in her chest.
Shizuka is Shizuru's younger sister who was born after Shizuru accidently erased her parent's memories. In the original Rewrite, they have never met but in Harvest Festa they are spoken to be very close to each other.
Touka dotes on Shizuru, alot; unexpectingly grabbing and hugging, much to Shizuru's displeasure. In school, Shizuru tends to avoid Touka due to her overly affectionate personality, when on missions with Guardian, Shizuru obeys Touka's commands since she is her superior. However, she occasionally disobeyed Touka due to boredom in Lucia's Route.
Esaka is considered to be Shizuru's foster father, their relationship is very good due to Shizuru always hanging out with Esaka's faction of Guardian. However, when she introduced Kotarou to Esaka she acted a little shy.
They are both members of Guardian and seem to be on good terms. There is not much communication between them.
Shizuru likes to hang out with Gen, she is a regular guest at his menra stand.
At first, her cluelessness was used as amusement for Kotarou, but as they got to know each other more she began to trust him enough to tell him about her past. As their relationship deepens she is prepared to sacrifice her life for him at the expense of her own. At the end of her route, she longs for him as she stays in a shelter.
The two never actually talked to each other much, but when Lucia and Chihaya were at each other's throats, she cooperated with Kotori and Kotarou in order to set them straight.
Shizuru's thoughts on Yoshino are dependent on what Kotarou tells her. When ever he says something misleading about Yoshino, Shizuru paints an estranged picture in her head. Example: Yoshino's head with the body of a giraffe.
Shizuru and Akane never really connected much throughout the story, the only times that they seem to have spoken is when they first met and at the end of her route.
They get along well together since they are both gluttons. Though they've never really hanged out with one another except when during activities with the club, their relationship is average.
Shizuru likes Sakuya due to the delicious food that he cooks. In her route, their relationship turned sour when Shizuru caught Sakuya choking Esaka when their base was attacked by Gaia. The two fought each other, fiercely afterwards.