Senna

Senna (茜雫, Senna) is a Shinigami girl met by Ichigo and Rukia in the real world during the events of Bleach: Memories of Nobody. She is also the main female protagonist of the movie, almost replacing Rukia and Orihime. Both of which had relatively minor roles in the story and less screen time.

Personality
Senna likes the color red and high places. She's also very curious, constantly darting from place to place. She is hardly ever serious, even when fighting. Later, she is shown to be very loyal when she sacrifices herself to save her friends, especially Ichigo.

Appearance
Senna has purple hair with a ribbon tied in it. She has large orange eyes and is usually seen in a school uniform. When she transforms into a Shinigami, Senna wears the standard unseated shinigami uniform with a large, red ribbon tied around her waist.

Synopsis
In Karakura Town, unidentifiable spirits begin appearing en masse. While attempting to deal with these strange souls, Ichigo Kurosaki and Rukia Kuchiki meet Senna, a mysterious shinigami who wipes out most of them. Senna refuses to answer any questions, so Ichigo is forced to follow her while Rukia tries to find out what's going on.

Meanwhile, in Soul Society, the real world is suddenly reflected in the sky, so Tōshirō Hitsugaya and Rangiku Matsumoto are sent to investigate. They meet up with Ichigo and discuss the events at the Urahara Shop, where Kisuke Urahara explains that a dimension between Soul Society and the real world, known as the Valley of Screams, has expanded to the point that it is connecting the two worlds.

The souls Ichigo saw earlier are known as "Blanks," souls that were lost in the space between the worlds and have been stripped of their memories. The Valley of Screams is composed of these Blanks, but they alone could not be responsible for the size to which it has grown. He goes on to explain that the lost memories of the Blanks will have formed into a single being known as the "Memory Rosary," and he has Ichigo track this being down.

Senna is eventually revealed to be the Memory Rosary, and a fair amount of the Gotei 13 shows up to deal with the problem. However, a mysterious group appears, identifying themselves as the "Dark Ones," and set their sights on Senna. Despite Ichigo's efforts, they succeed in capturing her.

Within the Valley of Screams, the Dark Ones attach Senna to a device powered by the Blanks. As concurrently explained by both the Dark Ones and Mayuri Kurotsuchi, the Blanks are naturally attracted to memories, which they lack. Senna, being composed of nothing but memories, will attract the Blanks, causing a chain reaction that will collapse the entire dimension. This in turn will cause the real world and Soul Society to collide, potentially annihilating both. The Dark Ones explain that their actions are to get revenge on Soul Society: they were shinigami over a millennia ago, but were exiled and have since adapted to the Valley of Screams.

Unwilling to give up on Senna, Ichigo finds the portal into the Valley of Screams on the river. As he enters it, Rukia heads to Soul Society to get reinforcements. Since the only available portal into the Valley of Screams exists in the real world, and the process that will destroy both Soul Society and the real world will complete within an hour, General Yamamoto orders that the Kidō Cannon be fired at the dimension to obliterate it first. Yamamoto refuses to order a rescue mission with such a tight time frame.

Within the Valley, Ichigo finds himself overpowered by the sheer number of Blanks the Dark Ones have at their command. He is saved by the timely arrival of Kenpachi Zaraki, with lieutenant Yachiru Kusajishi on his back. Aside from Zaraki, Soifon, Tōshirō Hitsugaya, Izuru Kira, Byakuya Kuchiki, Rangiku Matsumoto, Tetsuzaemon Iba, Shūhei Hisagi, Ikkaku Madarame, and Yumichika Ayasegawa have also arrived to help. The group makes short work of most of the Dark Ones, leaving Ichigo to battle their leader. Though it takes Ichigo longer and takes a larger toll on him, he is victorious as well.

Despite having stopped the collapse of the Valley of Screams, the process is far enough along that the effect persists. Senna, now in control of the Blanks, sacrifices herself to use their power to push the two worlds apart once more since she did not want Ichigo to die, thus saving the inhabitants of both Soul Society and the real world.

Extremely weak, Senna asks Ichigo to take her back to the graveyard so that she can see her name on her gravestone. Though the gravestone does not have her name, Ichigo tells Senna that her name is on it. Content that she once lived in the town and assured of her own separate existence, Senna evaporates. Rukia explains that once the power of the Blanks has faded, their memories of Senna will fade along with them. However, after the credits, Ichigo seems to vaguely remember Senna when the red ribbon he bought her floats down from the sky to him, and a girl resembling Senna is seen running past him.

Zanpakutō
Her zanpakutō, which Rukia reveals was lost 100 years ago in the severed world, is named Mirokumaru (弥勒丸, Mirokumaru? lit. Maitreya circle) and is released by the command "call forth the twilight". It takes the form of a shakujo when released, and has the power to create and control tornadoes.

Trivia

 * Senna was only seen in the movie Bleach: Memories of Nobody.
 * Senna is immensely popular among fans - even more so than Rukia - despite only appearing in the movie and never making it in the popularity poles, so far. So much so, that many fans wish for her to appear in the series, again.