Sachiko (nicknamed Sat-chan) is a friend and former next door neighbor of Akira Fudo's from before he moved in with the Makimura family. On her way home from a visit with him, she is killed and eaten by the demon Jinmen ending up as one of the faces on his shell. Accepting her fate, she convinces Akira to kill her so that he can kill Jinmen.
Sachiko is a preteen girl with long black hair and dark eyes. She is wearing a turtleneck jumper covered in stars at the time of her death.
Sachiko is sweet to Akira, but also seems to enjoy playful teasing. She apparently has a crush on Akira even calling him her 'almost lover', but he seems to either be oblivious to it or does not take it seriously.
She is first seen outside the Makimura home trying to ring the doorbell, but is too short to reach it. Miki Makimura surprises Sachiko by picking her up so that she can ring it. Sachiko is confused until Miki introduces herself, after which she shyly asks if Akira is home. Right after Miki asks who she is, Akira comes out and welcomes Sachiko in his arms. Miki asks again who she is, and Akira explains that she used to live next door to him and that they are close friends. Sachiko chimes in that they are almost lovers, resulting in a staring match between her and Miki, with Akira standing by confused. After their visit, Akira walks Sachiko to the train station, where she boards the 16:10 Shinkansen. Before they part, Akira makes Sachiko promise to never take the train by herself again.
While on the train, Sachiko notices the scenery change from a tunnel to a cave. She asks the man next to her where they were going, but he and the rest of the passengers begin to panic after looking outside. It becomes apparent that the train had been swallowed by a demon. The train guard then comes into the carriage and reveals himself as Jinmen. The passengers try to escape the train, but find the exit blocked off by a woman in a large coat, who immediately reveals herself to be the demoness Aleda. The two demons proceed to murder and devour every passenger on the train.
Soon after the train's disappearance is reported, Akira gets a phone call from Jinmen, telling him to meet him in a park. Akira arrives at the park, and sees Sachiko's face, shrouded in darkness, describing the gruesome details of her death and lamenting that she'll never be able to see her parents or friends again. Jinmen comes into the light making it that clear Sachiko is the center face on Jinmen's shell.
Akira transforms into Devilman and fights Jinmen, but Jinmen gains the upper hand by blocking Devilman's attacks with his shell. He tries to exploit Devilman's attachment to Sachiko and reluctance to harm the people on his shell. But Sachiko begs Akira to kill Jinmen, pleading with him not to worry about her as she is already dead. Taking Sachiko's words to heart, Devilman smashes his fist through Sachiko, completely destroying the left side of her face and killing her. Devilmen then closes Sachiko's remaining eye, allowing her to finally rest in peace.
Sachiko is seen in Hell, still attached to the shell of Jinmen. When Jinmen attacks Akira and Jun Fudo, Sachiko screams out to Akira. She berates him and asks why he tore her face off (possibly due to influence from Jinmen). Fortunately, she is saved when Devilman kills Jinmen, and all the souls in his body are released and presumably ascend to Heaven
- In Devilman: The Demon Bird, Sachiko is replaced by Akira's mother as the center face who tells Akira to end her suffering by killing Jinmen.