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|I just want to go home and farm.|
|— Sannagi on his family|
Sannagi was a young man with short black hair and thick eyebrows. He had a stocky build, and wears the standard Scout Regiment uniform within the films. His weapon of choice was an axe that he uses to slash through Titan's heels, putting them off-balance and bringing them down for the kill.
He was a mild-mannered, good at heart person who cared about his companions at the Scout Regiment and was capable of risking his own life in order to help his peers. He cared very much for his siblings, expressing a desire to go home and farm. While he had omni-directional gear, he often uses an axe in battle to slice a Titan's Achilles's tendon.
Sannagi has several younger siblings and lives on a farm in Yuen. He joins the Scout Regiment for unknown reasons, possibly to care for his siblings or as a dedication to humanity, and expresses a desire to return home and farm. One of his sisters, Koyuki, gives him a doll he accepts. He ties it on his ax, as a reminder to return home. When Jean and Eren get into a fight, he laughs at how the two are always fighting.
He says that when the Scouts go to Omotemachi, they will meet the Goddess of Shikishima's team, who was said to have killed at least ten Titans in half a year. The others laugh it off. When Armin gets confronted by a Titan, Sannagi grabs the Titan's arm and tosses it against a Wall. After Souda treats Jean's wounds, Sannagi asks why he hates Eren and Jean jokes that its because Eren's face looks like he is carrying the weight of the world's misery on his shoulders. Sannagi defends Eren by saying that he lost his girlfriend, Mikasa, to the Titans.
When morning comes and the Titans rise, Sannagi goes to the front lines and fights them with his ax. He cuts out the tendons in their legs, knocking them over so the others can take them out. He helps defend Jean, who gets stuck on top of a building swarming with Titans. After they are lured away, Sasha and Sannagi take out the Bearded Titan, with Sasha blinding it with her arrows and Sannagi crippling it with his ax. When Armin is grabbed by the Bloated Titan, Sannagi tries to cripple it, but for some reason, his ax is not able to break its skin. As the Rogue Titan appears from the corpse of the Bloated Titan, Sannagi wonders if its on their side and is one of the few recruits to see it as an ally. Sannagi is one of the subsequent recruits to see Eren emerge from the Rogue Titan's corpse and flocks around him amazed.
After Eren is taken captive by the Military Police Brigade, on suspicion of being a Titan, Sannagi tries to step forward in Eren's defense, but Jean tells him to stay for his own safety. When an Armored Titan appears and abducts Eren, killing numerous members of the Military Police and the Scout Regiment in the process, Sannagi and the recruits are left in awe at the sight of it. They are saved from the Titan only by the intervention of Mikasa, whose appearance miraculously causes the Armored Titan to cease his rampage and leave.
In the aftermath of the Armored Titan's rampage, as the recruits and Hans prepare for their trip to Monzen, Sannagi tries to convince a reluctant Jean to go with them, as they have a plan to seal the Wall.
As the recruits journey to Monzen to retrieve the inactive bomb on its outskirts, Sannagi asks Jean why he joined the scouts. Jean says he did not want to, the only reason he joined was because his father forced him. Sannagi, amused, breaks out in laughter, playfully commenting on Jean's misfortune.
Arriving at the site of the crashed bomb, Sannagi helps load it onto the recruits' transport vehicle, and they continue toward the Wall in Monzen. However, they are stopped in the middle of town by Shikishima and his militia. He is thrilled to see Eren emerge from one off the militia's tanks, alive and well. However, his excitement is short-lived as he and the recruits learn that Shikishima plans to use their bomb to destroy the second Wall, and utilize the Titans to overthrow the Royal Government. As Eren attacks Shikishima in a fit of rage, Sannagi and the recruits watch as Shikishima repeatedly beats Eren. As they look on, Jean and Sannagi decide to try to rescue Eren from Shikishima.
Sannagi, observing a damaged building nearbye, steps forward and tells Armin to go. Despite his misgivings, Armin agrees, and the recruits retreat with the bomb. Sannagi fires the anchors of his omni-directional mobility gear into the damaged building, and attempts to pull it over. Shikishima, amused, comments on Sannagi's strength, describing it as "the strength of a brute", before ordering his men to fire on Sannagi. As he dies, Sannagi give salutes his retreating comrades as the damaged building topples over, landing on Shikishima's vehicles and causing an explosion that engulfs Shikishima, Sannagi, and his men.
The group gets away, driving in the vehicle. Armin holds Sannagi's doll from his little sister and cries over his death as Sasha tries to console him.
- Sannagi was one of the few movie characters exclusive to the movie that is not a replacement for any manga character, the other being Hiana. However, he could be a condensed replacement for several characters, such as Conny Springer, who had a desire to make his family proud of him and to return home or Marco Bodt, who cared very much for his comrades.
- Sannagi and one other unnamed recruit were the only movie exclusive recruits to survive the events of the first movie. The other movie exclusive recruits, such as Fukushi, Lil, and Hiana, all perished.