皆城乙姫, Orihime Minashiro, Brunhilde System
Tsubaki is Soushis younger sister and is half festum due to thier mother bieng assimilated while still pregnant with her. As a result she spent her entire life in the coagulaa tube with luminescent liquid located in Valkyries Cave and serves as the core of the Brunhilde System. Having absolute control over the island she also expirences pain whenever Tatsumiya suffers damage in battle. When she left the cave she met a girl named Seri who was studying bugs and befriended her but had to return to the cave in the final episode as her body couldnt survive for more then three months outside the cave.