|Age:||17 years old|
|Cause of Death:||Fallen to her Death|
|Place of Death:||Kyoutoku Academy School|
|First Appearance||Last Appearance|
|Chapter 1||Chapter 7|
She was known as a very strong-willed character, who grew up with spending hours on end watching movies. One day, she snapped and realized how fake all the movies she wasted her time watching were. She founded the film club in the hopes of making realistic movies. She also would sleep with any man willingly.
Sanagi was a member of the film club at the same high school as Tomohiro Machiya and Mai Mashiro. Oushima is first introduced by as the next person Mai intends Machiya to film in his snuff films, claiming she will commit suicide in five days. This was facilitated by Oushima herself, who had Machiya film her and the rest of the film club on their field trip to the beach, ostensibly to film the next production for their film. Mai volunteered to accompany them on the trip and assist in production.
During their vacation, Oushima seemed to attempt to seduce Machiya, intentionally having him film her in a swimsuit and even while naked in a hot spring spa. During their time spent in the spa, the topic of Mai's claim that Oushima will commit suicide come up. Oushima replied that she would never commit suicide as she claimed to have a boyfriend- in spite of her apparently attempting to seduce Machiya.
On the day before Oushima was predicted to die, one of the members of the film club, a boy named Hikuchi, was found dead in the woods. After being questioned and ruled out as suspects by the police, Oushima talked with Mashiro, and implies Hikuchi was her boyfriend, and asks him to stop filming her. At that moment, Mai appears and attempts to convince Machiya to keep filming, but Oushima pulls him away along a seaside pathway.
In the woods, Oushima reveals she got a text message from Hikuchi's phone demanding she commit suicide or more of her friends will be murdered. As they walk along the path, they see two more members of the film club, Taniguchi and Ootomo dead, having been thrown from a sea cliff. At this, Machiya reveals that he witnessed and filmed Mai commit a murder once before. Machiya and Oushima also note that Mai has somehow manages to evade detection by the authorities.
After ruling out faking Oushima's death after a lengthy discussion Machiya and Oushima agree to attempt to eliminate or capture Mai, and Machiya goes back to the hotel. After he takes a bath, however, Machiya receives a text telling him to meet with Oushima.
Outside the hotel, Oushima received a message from Mai containing a video of the rest of the film club held captive. The video also shows a girl named Mizuno being raped by two unidentified male accomplices.
Oushima then redoubles her attempts to seduce Machiya, allowing him to grab her breast to show him how fast her heart is beating. Meanwhile, Machiya suspects something is off about the whole scenario, and receives a mysterious call from Mai.
Oushima leads Machiya onto the school roof and positions herself as though about the jump. Just before Mai arrives, Oushima kisses Machiya and confesses her love for him. Machiya then hides behind the door to the roof with a baseball bat, but when Mai arrives with a camcorder, she knows he is there. She warns him not to make any "sudden movements" and urges Oushima to jump.
At that moment, Mai is tackled by a still half-naked Mizuno, claiming to be the lone survivor of Mai's killing spree. Mai, however, throw Mizuno off her, against the fence surrounding the edge of the roof, knocking Oushima off the roof.
Machiya sees "Oushima's" bloodied corpse on the ground, and flies into a rage, and beats Mai apparently to death with the baseball bat. After Machiya kills Mai, two film club members, boys named Takahiro and Moto reveal their presence, and Mizuno reveals that that both they and Mai are members of an illegal snuff film sharing site called Dead Tube, and that they intend to win prize money from the site.
Oushima then walks back on top of the building and reveals that she did not actually fall to her death, but landed safely on an mattress on the floor below, and that she threw their drugged club member Miiko Yamada off the building and killed her instead. Oushima also revealed that she killed the other three dead members of the club as well. Higachi, Taniguchi and Ootomo even willingly agreed to die in exchange for getting the chance to rape Mizuno. Oushima also reveals that, since Machiya joined the film club, they had intended to make this film. She also stated that she was sexually involved with both Takahiro and Moto, and never really loved him. Oushima encourages Machiya to commit suicide after being told his entire high school life was lie.
But Machiya simply replies "too bad" and reveals that he faked Mai's death using a foam bat and fake blood. Mai gets up and murders Takahiro, Moto, and Mizuno. At this point, Oushima begs for her life, undressing and offering Machiya sex in exchange for convincing Mai to spare her. Mai respond that she will spare her life if she licks Machiya's shoes.
Mai, however, is quickly proved to be lying. She instead restrains Oushima and hangs her by the ankles over the edge of the school. Mai then cuts the rope holding her and Oushima falls to her death as Machiya films her.