After a deadly disease wipes out the moon colony, Kyosuke Date and his mother escape to Earth, seeking safety in a cathedral where his mother assumes the role of a mysterious nun. Tragedy strikes when attackers invade their haven, leading to a shocking betrayal. Kyosuke miraculously survives, only to awaken in the care of a girl who claims to be his twin, Runa. Unraveling a dark secret, they discover that Runa's soul has fragmented into 'flicker girls' hunted by the malevolent Kirihara Group. Kyosuke, transformed into the powerful SoulTaker by a unique genetic response to the disease, embarks on a perilous journey to confront evil mutants and corporate foes, all while striving to protect his newfound sister and unearth the truth of their intertwined fates.