Second oldest of the 4 Isumi sisters. Head of squad A-01, Isumi's Valkyries.
Isumi makes her first debut during the Yokohama Incident where Eishi pilots were testing the XM3 until BETA forces appear in the training area. Later this leads to a lot of deaths including Sgt. Jinguuji among the casualties.
Like Shirogane Takeru, Isumi was also a student of Sgt. Jinguuji. She admitted at a point in her training that she and her squad loathed Marimo especially after the training incident that got one of Isumi's squad mate killed. Isumi explained how she angrily went to give a good beating on her superior only to find Marimo crying in her room. Later, she and her squad nicknamed Marimo the "Mad Dog"
She later becomes the instructor for Takeru as he had missed on a lot of lessons on the BETA. She helps Takeru a lot by sending him through psychological therapy due to his traumatic experience from the Yokohama incident.
Before the Battle of Sadogashima, Isumi is one of the Eishi Shirogane talks to. Isumi explains her background story on family and her lover. Takeru then explains his situation about Sumika which infuriates Isumi making her demand that he survives through the battle no matter what.
In the Battle of Sadogashima, the 00 Unit/Susanoo malfunctions which Isumi volunteers to enter the Susanoo and self destruct or restore it;however, program errors prevented her from activating the autopilot of the Susanoo II as originally planned, and Yuuko ordered her to settle with getting the self-destruct up and running. However, the sudden appearance of fresh BETA forces underneath the Susanoo II, and headed towards the mainland in their advance, forced Yuuko to call for Isumi's evacuation and for the ships of Echo Unit to bombard the XG-70b.
As the rest of the Valkyries retreated, Kashiwagi, who was holding off the BETA with both her unit on automated control and her in Isumi's Type-94, was overwhelmed in combat and killed by a direct hit on her cockpit from a Fort-Class BETA . Foreseeing no other escape, Isumi recommended staying back to try activating the self-destruct function of the Susanoo II. Later the self destruct sequence took too much time where the BETA surrounded the unit leading to Isumi's final decision of manually self destructing it. She talks to both Yuuko and Shirogane Takeru in her final moments where Yuuko informs her that her sister survived the battle. As for Shirogane, Isumi apologizes that she couldn't try the Hot Spring method on the man she loved. Afterwards, she detonates the Susanoo's self destruct sequence, annihilating both the BETA and herself.
The aftermath of Operation 21 destroys the Sadogashima hive and island, causes a tsunami to the northern regions of Japan (Niigata), and later leads to the BETA attack on the Yokohama Base.
Later Hayase becomes the new leader of the unit and decides that the name "Isumi's Valkyries" will stay as is in honor of Michiru's sacrifice.
"It's far more important to keep those still alive from being killed than to mourn the death of those who've died."
"Achieve your mission with all your might.
Despair not until your last breath.
Make your death count!" - Isumi's Valkyries"
