Daichi Tsutsumi/Plot

Background
Tsutsumi joined Border three years before Yūma Kuga and Chika Amatori. In the time he has known Nozomi Kako, he has become ill after trying two of her fried rice recipes: mint chocolate fried rice and honey-smelt fried rice.

Introduction Arc
Suwa Unit presumably takes part in the extermination of all Rads in Mikado City.

Border Enlistment Arc
On January 8 Tsutsumi and Kōtarō Suwa oversee the simulation mode for the new recruits. Suwa is unimpressed with their skills, although Tsutsumi points out that it is only by comparison with a few stellar rookies from past enlistment days. They are blown away when Yūma defeats the simulated Bamster in less than one second. When Sōya Kazama challenges B-rank Osamu Mikumo, Tsutsumi wonders if there is a connection with Yūma and serves as the announcer. When Osamu asks for one more match after his 20 defeats, Suwa comments that he would rather see Yūma fight, but Tsutsumi counters that he would like to continue watching Osamu, sensing that something in him has changed. After starting the battle Suwa and Tsutsumi are riveted by Osamu's tactics. Tsutsumi announces the latter's defeat, but corrects his verdict when he notices that Kazama has suffered a lethal trion leakage. He thus declares the last round a tie.

Large-Scale Invasion Arc
Suwa Unit is deployed by Masafumi Shinoda to prevent the initial wave of Trion Warriors sent by Aftokrator from reaching Mikado City. Border's traps buy them enough time to arrive on the scene. A Rabbit emerges from the carcass of one of the defeated enemies, its armor resisting Suwa's and Tsutsumi's bullets. When Hisato Sasamori is stunned by the Trion Warrior, Suwa covers Tsutsumi as he rescues their teammate, only to be captured and stored inside the Rabbit. Tsutsumi and Sasamori are saved by the timely intervention of Kazama Unit and are dispatched to fight Trion Warriors in other areas. When Kazama Unit manages to kill the Rabbit, they find out that Suwa has been turned into a trion cube. Kazama tasks Tsutsumi and Sasamori with bringing it to HQ for analysis.

After some initial difficulties, the engineers succeed in reverting the cubification in time for Suwa to intercept Enedra as he rampages inside the base. His Black Trigger appears to make him immune to damage, but Kazama observes that his trion body must possess a relay center and a supply system and that Suwa Unit's shotguns are ideal for finding them. Suwa and Hisato lure Enedra into one of the training rooms while Tsutsumi operates it, activating the simulation mode an instant before Enedra can finish off Suwa, trapping the three in the room so as to prevent him from causing any more damage as well as giving Border time to find the Neighbor's weak point. One of Suwa's bullets eventually hits a hardened shell, which Tsutsumi marks. The Border agents realize that it contains Enedra's vitals, but the Neighbor creates several dummies hide it. After Enedra unwittingly turns off the simulation mode and breaks out of confinement, Tsutsumi moves to help his teammates but is preceded by Shinoda.

At the Director's command, Tsutsumi turns on the air conditioning to blowback the Neighbor's gaseous attack. When, however, the latter fakes his defeat and immobilizes Shinoda, Tsutsumi rushes to support Suwa. They hit the shell containing Enedra's vitals before he can create his decoys and have Rui Osano activate Starmaker to mark it. When the Neighbor foils Sasamori's sneak attack, Suwa and Sasamori pretend to use the smoke caused by the destruction of his trion body when in reality it is Shirō Kikuchihara and Ryō Utagawa, who had been hiding with Chameleon the whole time, who deal the critical blow. Just then Mira opens a wormhole and, to everyone's shock, cuts off Enedra's hand to retrieve Vorvoros and kills him. Tsutsumi and Suwa are subsequently stationed outside of the base and see the last of the Gates close.

After the end of the invasion Suwa Unit is the recipient of an Excellent Distinguished Service award.

B-Rank Rank Battles Arc
On February 1, Suwa and Tsutsumi survive their battle against Suzunari First, defeating the powerful Kō Murakami with their combined firepower and Sasamori's obstruction of the enemy.

Round Two
The following day, three days before their match against Tamakoma Second and Arafune Unit, the members of Suwa Unit gather to prepare a strategy in HQ's cafeteria. Suwa remembers that Yūma is a member of Tamakoma Second and Tsutsumi adds that Osamu is too. They watch the logs of the unit's first rank battle and are shocked by Chika's firepower, with Tsutsumi also taking note of Yūma's skill and commenting that, as Reiji Kizaki's pupil, Chika should have mastered the fundamentals of sniping.

On February 5, when Tamakoma Second's map of choice is revealed to be Cityscape C, Tsutsumi remarks that it will be a difficult battle. The members of the Suwa Unit convene to start the match by regrouping. Tsutsumi spawns a little north-west of the center of the map and immediately starts running eastward towards Suwa, meeting up with him before the latter saves Sasamori from Atsushi Hokari's pickoff attempt. The three are pinned in place until Tamakoma Second draws Arafune Unit's attention, at which point Suwa attempts to ambush Tetsuji Arafune. When Yoshito Hanzaki gives away his position, Tsutsumi targets him, succeeding in taking him out before Yūma can. He attempts to anticipate the Attacker but is surprised by his use of Grasshopper and ends up bailing out. Reflecting on his mistake, he apologizes to Osano. He continues following the match from her terminal and attempts to warn Suwa about Osamu's attack, but his captain fails to react in time and is eliminated. His teammates tease him for not scoring a single point. As a result of the match, Suwa Unit drops to 10th place.

Galopoula's Blitz
On the night of February 19 Tsutsumi is assigned to the half of close and mid-ranged fighters led by Suwa during Galopoula's incursion. They move forward to intercept the Idras, but the Dogs summoned on the roof by Koskero deprive them of the Snipers' cover and force them to fall back. When Kizaki, Arafune, Shun Midorikawa and Shinnosuke Tsuji repel the Dogs and the Snipers are freed up, the Gunners manage to push back the Idras. Tsutsumi urges Kako to lay off Masataka Ninomiya when he takes command. With part of the Snipers relocating to the ground level, the close and mid-ranged fighters start to advance as they mow down the Trion Warriors. Tsutsumi takes the left side of the wedge formation consisting of him, Suwa, Sasamori, and Tatsuya Kuruma in one of the most forward positions. They are suddenly targeted by an unusually powerful Idra, and although Sasamori manages to foil the flanking attempt, Suwa and Tsutsumi fail to hit it. With Sasamori and Tsuji facing off against it, the two Gunners are free to go back to engaging the other Trion Warriors. They later ignore Reghindetz's feint. After the enemies retreat, Tsutsumi, together with the rest of the ground forces, remains inside the security zone for a while.