Satoru is a childhood friend of Saki, as well as a fellow member of Group 1. They have been seen to always argue with one another but are very close otherwise, as seen in many instances throughout the series. The two even became each other's duty partner (a public declaration of love). After the timeskip, they apparently had an argument and stopped talking to each other until an incident with the queerats causes them to reconcile. In the manga, their relationship is more developed; Satoru originally had feelings for Shun (who Saki also loved, however Shun only reciprocated feelings for Saki), but as Group 1's members died off one by one, and as the two spent more and more time together, Satoru and Saki eventually realize their feelings for each other. Ironically, it is Shun (who is still alive in Saki and Satoru's subconsciousness) who pushes them towards each other. Saki eventually realizes that even though Maria and Shun are gone, there is someone who has always been more important and dear to her - Satoru. He would later replace Shun and Maria as the most important person in Saki's life. During the crisis with the fiend, Saki tells Satoru she would like to build a new future with him, as well as have a child with him. After the death of the fiend, Saki and Satoru marry (which now makes her Saki Asahina), but this scene is not present in the manga. The series concludes with Saki pregnant with Satoru's child, hoping for a brighter future.
Shun is a childhood friend of Saki as well as her first love who loved him very much that she was willing to go to great lengths for him: even skipping school so she can find the bungalow (a field in the manga) where he is hiding in. As seen in the manga, the two first met when they both agreed on seeing auroras and other beautiful natural wonders outside the holy barrier one day. Shun and Saki confirm that this is when they first fell in love with each other. When she learnt of Shun becoming a karma demon, she blamed herself as though it was due to not being able to restore his Cantus properly. After his death, he appears in her dreams as a faceless person, as his name has been forgotten by her and the rest of Group 1. He guides her when in times of trouble and was the key instrument for Saki to realize how to defeat the fiend. In the manga, Saki finds herself having a difficult time reciprocating Satoru's love, but she realizes (thanks to Shun) that neither Shun or Maria are the most important people to Saki anymore. Realizing her hidden feelings for Satoru and his heavy importance in her life, Saki says farewell to her beloved Shun and lets him go.
Maria is a childhood friend of Saki. They are hinted to be very close, as they were friends even before the group's formation. After they had turned 14, Maria and Saki began a romantic relationship, although they had participated in intimate acts with each other before this. They have been shown to be intimate and loving to each other, although it is implied this is due to the humans attempts to incorporate bonobo's loving nature and habits (including homosexual relationships) into the human genome, in attempts to create a less stressful and violent environment. Despite that, Saki loved and cared for Maria; Maria reciprocated these feelings. When Maria and Mamoru leave the group, Saki is incredibly saddened, and does everything in her power to find them. However, Saki puts her search to an end when Shun (who is known as "the faceless boy", or "X") appears in her dreams and tells her that Maria must die. Years later, Saki is devastated and distraught when she learns of her death. In the manga, Shun hints that he and Maria were once the most important people to Saki. The manga also reveals that Maria had felt her happiest with Saki, and as thus asked Mamoru to use his Cantus to draw portraits of her only when she was with Saki.
Mamoru is a childhood friend of Saki. Saki appeared to be aware of Mamoru's feelings for Maria (her girlfriend at one point), but flaunted their relationship in front of him anyway, although she does encourage him to find someone else. When Mamoru and Maria leave the group, Saki is distraught and later has a difficult time accepting their confirmed deaths. In the manga, she has the drawings Mamoru drew of Maria and Saki all over her walls.
Reiko is a childhood friend of Saki. The manga implies that Reiko, Saki and Maria were all friends before the group's formation. She also apparently took part in Saki and Maria's intimate activities. Both the manga and anime reveal that Saki misses Reiko dearly, even if her existence is wiped from her memory at one point.
Mizuho is Saki's mother who were shown to be very close. Saki's mother was very protective of her, as it is implied she had many previous children taken away for various reasons. She strictly enforces the village's rules onto Saki, hoping that she would not suffer the same fate as her siblings before her. During the queerats invasion, Saki's mother leaves her a box disclosing secret information about the Psychobuster. While it is later revealed that Mizuho and her husband perished in the Fiend's rage, Saki remembers their legacy and believes that they did not die in vain.
The chosen filler for the void Shun would leave, as he committed suicide after transforming into a Karma Demon. While Saki initially believes he is the boy she loved ever since childhood, she later realizes this is not the case. Although the two wanted to be duty partners, Saki later decides not to be with him and chooses Satoru instead. Ryou is shown to be upset about her decision, but he manages to find another girl to be duty partners with.
Tomiko was the Head of the Ethics Committee (before she is succeeded by Saki), which is considered the highest authority, even surpassing the Board of Education. The two first meet when Saki is fourteen years old. Tomiko had very high hopes for Saki to take her position, after confirming that she had the qualifying traits (high Personality Index Score, ect); she was willing to disclose rather secretive details to Saki. The two appeared to be very comfortable with each other, even upon their first meeting. Over the years, Tomiko would train Saki for her future position. Tomiko would later leave her village's future and position to Saki; entrusting a way for her to find a way to defeat the Fiend. Tomiko would later die from her injuries (although this was not shown in the anime) from her encounter with the Fiend. Through marriage to Satoru Asahina (Tomiko's grandson), Saki became Tomiko's granddaughter-in-law.