The Truth of Yomijima M3: Sono Kuroki Hagane : Season 1 Episode 18

To research the secret of the Arbornine that prevents the Necrometal infection from spreading, Suzaki, Akashi and the others secretly headed over to Yomijima, the island where Minashi and the two girls were born. The memories of the massacre that happened in the now ruined IX laboratory flooded into Minashi. Just then, Natsuiri, who had chased the group to the island, shows up together with the "very first MA-Vess.”