Rikka Sakuragawa (桜川 六花, Sakuragawa Rikka) is Kuro Sakuragawa's older cousin and the reason he visited the hospital as regularly as he did. Just like Kuro, she also has the powers of immortality and precognition, although she wants them to be removed and has tried medical science and suicide to no avail. Due to this, she later switches her plan on creating imaginary monsters such as Steel Lady Nanase with god-like powers, hoping that they would eventually be able to turn her back to normal.
Rikka is a tall woman, with short dark hair that fans out from her face, and a thin, malnourished frame. Despite her sickly appearance, she is still seen as beautiful.
She is a seemingly calm woman with an ethereal presence. In truth, however, she is a determined and ruthless woman with no regard for her own safety, much less anyone else's.
As a child of the Sakuragawa family, she ate Kudan and Ningyo meat as part of the family's goal of creating someone who could predict the future without dying. She was one of the survivors along with Kuro.
Later on in life, she is admitted to the same hospital that Kotoko Iwanaga goes to for her checkups. Kuro regularly visits her during her time there, later accompanied by Saki, his girlfriend at the time. She later gets into painting during her stay at the hospital.
Eventually, she wants to move out and live with Kuro, but instead moves in with the Iwanaga family after he calls Kotoko to explain the situation. Her residence there doesn't last long before she mysteriously disappears.
Rikka was the one who created the monster the Steel Lady Nanase. Using her abilities she is able to create the Steel Lady Nanase wiki and redirect the thoughts and fears of the people online so that the supposed phantom can retain her power.
After the steel lady arc it is concluded that Rikka is actively using her powers in an attempt to go back to being a normal human being. She creates these monsters of the imagination, a being with god-like powers, for her sole purpose of being normal. It was also concluded that the reason why she was at the hospital for so long to see if medical science would help.
Ghost Creation: Through strange means, Rikka is able to create spiritual beings based on the untimely death of famous people. In Steel Lady Nanase's case whose model is based on the idol Karin Nanase, she firstly creates an online forum called "Steel Lady Nanase Wiki." Then, from a picture she painted, Rikka begins spreading the rumours to the public, from person to person until eventually it took on a life of its own. Additionally, the creature she created is immortal, since their life lies not within the body but within the countless desires that have given their form its flesh.
Immortality: Just like Kuro, since she had been fed both Kudan and Ningyo meat, she possesses the same abilities as her cousin. During the Steel Lady Nanase's Arc, she was frequently seen committing 'suicide', only to recover and wake up from her sofa right after. She demonstrates her healing ability again in Chapter 23, after getting hit by a truck, she quickly heals herself.
Precognition: Rikka has also the power to determine the future just like Kuro. However, when she tries to use this power during "Dueling Fictions", she is being interupted by her cousin who used the exact same ability as her. As a result, she is unable to grab the future she wants.
Kuro Sakuragawa: As her younger cousin and someone with the same abilities as her, they have an understanding of each other but not necessarily a good relationship.
Kotoko Iwanaga: When they first meet, Rikka tells Kuro that Kotoko "isn't a good one," only for him to say that he agrees. After the awkward situation, Rikka tries to take back her statement. Rikka later resides at Kotoko's home and the two had good times before the former disappeared mysteriously, starting her agenda for the Steel Lady Nanase's plot.
Saki Yumihara: Saki had hard times to visit Rikka when going to the hospital with Kuro, although eventually asked him to make a visit once. During that meeting, in contrast to when she met Kotoko, Rikka was very cordial to Saki and told Kuro that she was "a good one". Upon their meeting, Saki recognizes that she slightly resembles Rikka, stating that Kuro's type "can't be more obvious" and asks if it was also the reason he wants to go out with her. Kuro later admitted his feelings for Rikka but states that he also wants her out of this world. Saki had mistaken Rikka for being dead, only for Kuro clarifies that she is not dead and never will. Realizing the elder Sakuragawa is also immortal, Saki was left fazed.