Shiina Kagari is the adopted daughter of Shiina Mayuri in 2036 in the Beta 1.129848% World Line.
Kagari has a slender build, with long red hair, pale skin, and blue eyes. She greatly resembles Kurisu Makise, though any potential connection between the two is not explored in depth.
In the year 2028, Mayuri is working at a children's orphanage and given custody of a young girl. Because of the war the girl's family register was lost and her true full name unknown. Over time the child grew to view and love Mayuri as her own mother. Mayuri gave her the name "Kagari" -a reference to "kagaribi（篝火?)", meaning bonfire-, with the wish that Kagari would be a shining light to everyone no matter how dark the world line is.
She was adopted by Mayuri in 2034, and in 2036, she time traveled with Suzuha Amane to the past. However, Suzuha and Kagari became separated in the year 1998, causing Kagari to have grown into a 22 year-old woman by the year 2010.
In Steins;Gate 0's Altair & Vega route, Kagari Shiina had plastic surgery to look like Yuki Amane. It was revealed that the original Yuki Amane is safe and is studying in Europe.
She was among the people experimented on by Stratfor and is brainwashed. This is the reason for her amnesia. Stratfor referred to her as "K6205", which is code for the fifth sonata of The Magic Flute by Mozart, the melody which awakens her brainwashing.
- Kagari features in Steins;Gate 0 and the light novels and manga adaptations of Epigraph of the Closed Curve, Pandora of Eternal Return and Altair at the Apoapsis of Infinity.