Isuka Suginami (杉波 伊砂 Suginami Isuka) is Ikaruga's "twin" sister who was previously affiliated with the Alchemists before allying herself with Valhalla after promising them to revive the mythical dark elves.
Isuka is visibly identical to Ikaruga and shares the same bodily proportions with a shapely figure and long hair. Instead of Ikaruga's brown hair, Isuka's is red and she wears a matching red lab-coat with a black tie and shirt underneath.
Isuka in her early days was extremely content with researching and developing with Ikaruga and showed enthusiasm and youthful exuberance. She also exhibits stubbornness in going against their purpose to continuously innovate and became spiteful when Ikaruga left her. After many years alone, Isuka became further embittered about being abandoned (but slightly regretful in not following) and her punishment from her superiors had her emotions and thoughts suppressed. Fittingly, she still knows very little about how the outside world works and her lack of "humanity" surprised Haunted.
Ikaruga and Isuka were created in an Alchemists facility as the "Suginami Design Children" to solely work on manufacturing and producing scientific breakthroughs, with their current goal being to revive the dark elves, who went extinct after the first Witch Hunt War. Both of them were never let outside and knew nothing of basic human interaction and morality other than caring for themselves and for each other. While they were born in the Alchemist's primary lab, they were transferred to the 5th Laboratory. On a fateful day, Ikaruga began reading a book and grew an interest in knowing about the outside world and Isuka tried to talk her sister out of dangerous thoughts and return to their daily routine of research and development. Ikaruga's growing obsession with the outside world eventually culminated in the eventual creation of Kanaria, a wood-elf infant with no magical ability that Ikaruga intentionally created to have herself be evicted. Eviction however was only for other alchemists, for Design Children who failed, only execution awaited them.
Ikaruga finally decides to escape from the facility and wanted Isuka to come with her. Isuka however refuses to leave with her and Ikaruga runs off alone, while also taking the Lost Matrix with her. With Ikaruga's departure, Isuka was spared from death after being deemed to valuable and was punished with further modifications to her body where she was only able to make a limited amount of facial expressions and intense headaches with she felt an emotion she wasn't supposed to. She was also burdened with nurturing Kanaria.
Two Alchemists ArcEdit
Isuka is seen inside the 5th Laboratory near the Inquisition controlled border areas where she meets with Haunted, who previously murdered everyone inside the laboratory under her request. Isuka had broken off from the Alchemist's faction in order to pursue her own work and joined with Valhalla to resurrect the dark elves, a goal that would sate both her and Valhalla's wishes. Isuka's lack of empathy and the value of human life turns Haunted off and he ironically demands Isuka to feel some emotion when she is responsible for killing somebody. On the other side, Ikaruga disguises her intent to reunite with Isuka and return the Lost Matrix by lying to her platoon that she'll be leaving to watch the dragoon race. Ikaruga is branded a traitor by the Inquisition in Sougetsu's attempt to wage war against the Alchemists and the 35th platoon head out to track Ikaruga down of their own accord.
Isuka sets up a few check points to escort Ikaruga with her mercenaries but the 35th Platoon's interference leads to a separation. Isuka's mercenaries are able to capture Usagi, Mari, and Ouka and Ikaruga is able to bargain with her their safety in exchange for the lost matrix to which she agrees. They are soon reunited after Ikaruga is picked up on her chopper after the latter drugs Takeru. While a small war wages outside, Isuka demands to know why Ikaruga left and asks if whatever she found out there was worth it, to which Ikaruga explains that she simply grew out of the mindset of wanting to mindlessly create weapons. Ikaruga adds that she fully intended on taking Isuka with her. Isuka however declares that she found her own way out of the Alchemist's hands and her reason for joining Valhalla was to fulfill her research to recreate dark elf and break her imprisonment. The key to her freedom lied with the Lost Matrix and Isuka demands for Ikaruga to return it to her, but receives a completely unexpected result. Utilizing its data, Ikaruga was able to create a modification to her own body which rewrote her genes to temporarily turn herself into a dark elf. Ikaruga expresses her intent to destroy the facility and take Isuka back with her and the latter begins to feel a glint of hope and sorrow, to which Haunted immediately responds to. Haunted leaves a fatal wound while Ikaruga attempts to fight back. Haunted disappears and Isuka comforts Ikaruga who apologizes for her actions and reveals that Kanaria was kept alive. Isuka's body fades away due to Haunted's attack and the latter reappears to express his joy in finally seeing emotions out of her. Haunted soon disappears again after he explains that Isuka became disposable after he learned vital information from her weapons schematics. With Haunted's magic eating away her body, Isuka tells Ikaruga in her dying breath of Kanaria's survival within Valhalla and forgives Ikaruga before disappearing.
Design Child: Like Ikaruga, Isuka was born as the result of the Alchemist's Design Children project to genetically engineer prodigies to advance the world's scientific progress. While Ikaruga fled the facility, Isuka was further modified by a process called "reeducation" where had her emotions suppressed to not interfere with her research.
- Inventor: Having spent most of her life developing weapons schematics, Isuka is a prodigious weapons designer and she was responsible for the method of simplifying the creation of magic-based Dragoons that Valhalla would soon adopt as their main method of troop deployment. Her intelligence also placed her as the lead researcher in resurrecting the dark elves, as well as other projects such as schematics for constructing mechanical dragons.
- Like the other Suginamis, Isuka is named after a bird. In her case, a crossbill.