Tetsuji Arafune/Plot

Background
When he was younger, Arafune was bit on his right butt cheek by an unprovoked small dog, bearing the scar to this day. The incident caused him to dislike dogs.[BBF Q79] Arafune joined Border around two years before Yūma Kuga and Chika Amatori, starting out as an Attacker. His approach to improving, which remain unchanged when he would later transition to Sniper, consisted in watching the logs of other agents of the same position, creating theories, testing them in rank battles, and seeking guidance only if after sustained trial and error he was unable to understand what he was lacking.[BBF Q76] He was still an Attacker when Arafune Unit was formed.[BBF Q79]

A little over a year and two months before his unit's match against Tamakoma Second and Suwa Unit, Arafune began teaching swordsmanship to Kō Murakami. Less than seven months later Murakami surpassed Arafune in points. Around the same time Arafune reached Master Class as an Attacker and became a Sniper. This caused a rumor to spread among Snipers that Arafune had changed position due to being surpassed by Murakami, whereas in reality Arafune had always planned on quitting after scoring more than 8000 points with his method, his ambition being to become the first Perfect All-Rounder after Reiji Kizaki and to develop a master theory that would allow the mass production of Perfect All-Rounders. He did not share his goal with anyone out of fear that it would sound like an excuse. However, the rumor caused Murakami to fall into depression, causing Tatsuya Kuruma to meet up with Arafune to ascertain the truth. Arafune explained his aim to Kuruma and send Murakami a video to put his mind at ease. Not much later Arafune also started weight training with Atsushi Hokari.[BBF Q128]

Border Enlistment Arc
Arafune appeared alongside Haruaki Azuma as one of the Sniper instructors on enlistment day. He is surprised that trainee Chika Amatori already knows that Snipers have to run after firing.

Large-Scale Invasion Arc
Masafumi Shinoda orders Arafune Unit and the other B-rank squads on active duty during Aftokrator's invasion to meet up with Azuma. Arafune, Hokari and Yoshito Hanzaki take sniping positions while Azuma lures Lamvanein towards them. The Neighbor however blocks their bullets and retaliates. Arafune manages to dodge the attack but his two teammates bail out. As he repositions himself after another failed ambush, he observes that Lamvanein seems to leave himself completely exposed to draw in the shots. When A-rankers Kōhei Izumi, Shun Midorikawa and Yōsuke Yoneya are dispatched to assist the B-rank units against the Neighbor, Arafune warns them that his defenses can withstand Eaglet shots and might be able to resist Attacker Triggers too. When Lamvanein takes to the sky Arafuna manages to damage his Trigger. He jumps off the building to avoid Lamvanein's counter, but the Neighbor waits a few moments before firing a follow-up shot, tearing off Arafune's left arm. The Sniper remarks that Lamvanein's accuracy has increased and that the Border agents can no longer get close to him, but Azuma objects that they must remain on the offensive to force him to show more openings. Following the Neighbor's defeat, Arafune is reassigned to defending the southern area of Mikado City. After the end of the invasion Arafune Unit is the recipient of an Excellent Distinguished Service award.

B-Rank Rank Battles Arc
On February 2, three days before Arafune Unit's match against Tamakoma Second and Suwa Unit, Arafune, Hokari and Hanzaki watch the logs of Tamakoma Second's first rank battle. Arafune notes that Chika will be easy to snipe back at if she fires with Ibis and instructs Rin Kagami to gather all the data on the members of Tamakoma Second so that he can memorize their habits. He then wonders which map they will choose.

When the stage, Cityscape C, is announced, Arafune warns his teammates to watch out for Chika and tells them to go about the match as usual. He spawns to the southernmost point in the map, already wearing his Bagworm. Thanks to Hokari's suppress fire, Arafune manages to slip past Suwa Unit. One of Chika's Ibis bullets explodes right next to him, causing all of Arafune Unit to focus their fire on the gathered members of Tamakoma Second. While they do so, however, the members of Suwa Unit activate their Bagworms and close in on the Snipers undetected. Arafune's leg is injured by Kōtarō Suwa's sneak attack. Arafune withdraws with Suwa hot on his heels. Arafune draws him in to be sniped by Hanzaki, but Suwa anticipates it and blocks the bullet. He and Hisato Sasamori continue pursuing Arafune while he intercepts Yūma Kuga, confronting him with his Kogetsu and keeping his Bagworm on to conceal the wound on his leg. As he clashes with Yūma he takes note of his opponentss skills and predicts that Suwa will come for both of them. When Hokari blows off Yūma's shoulder in a suicidal attack and the Neighbor activates Grasshopper, Arafune moves in to land the finishing blow, but Yūma feints and cuts off both his legs. He manages to slip away thanks to Suwa opening fire and focusing on Yūma. When Chika devastates the area around her teammate, Arafune snipes at her, picking her off before bailing out himself due to losing too much trion. He apologizes to his teammates for being unable to defeat Yūma. He reacts with surprise to the announcement that one of Tamakoma Second's upcoming opponents will be Suzunari First.

Arafune heads to the solo rank booths after the match, where he runs into Yūma and Midorikawa. He puts the latter in a headlock for foreseeing his defeat in his commentary and challenges him to a solo match. He greets Murakami when he arrives and the two chat for a little while before Yūma challenges the no. 4 Attacker. Arafune is the first to warn him against doing so, but when Yūma goes through with it, he watches the match. Afterwards he has a match against Yūma himself.

During stealth and target acquisition training Arafune is shot in the head by Isami Tōma without being able to retaliate. He finishes the session in 7th place. He is dissatisfied with his result and he approaches Hokari.

Arafune is assigned to the half of official Snipers led by Tōma in preparation for Galopoula's blitz. The Snipers are all stationed on the roof of HQ. When the Idras combined their shields, they begin to focus their fire. Koskero summons dozens of Dogs on the roof, prompting Arafune and Kizaki to fight back with their Attacker Triggers. Together with Midorikawa and Shinnosuke Tsuji they proceed to exterminate the Trion Warriors, allowing the other Snipers to resume their positions. When the roof is cleared, Arafune Unit, Kizaki and Ken Satori jump off to assist the agents on the ground. As they gain th eupper hand, Arafune wonders if Galopoula has more aces up its sleeve. After the enemies retreat, Arafune, together with the rest of the ground forces, remains inside the security zone for a while. He asks Kizaki if they are done, to which the latter replies that they will probably not try anything while there are still Border agents around, but warns Arafune not to lower his guard.

A few days later Arafune and Hokari run into Yūma, Tōma, Murakami, Yuzuru Ema, Hiro Kitazoe and Masato Kageura at the latter's family restaurant. When they explain Ema's predicament to him, Arafune explains that all Ema needs to do is be selected as a member of the away team to protect Chika. Later, he asks if it is true that she cannot shoot people, and understands that is why she started using Lead Bullet. He listens to Tōma's theory about Chika not wanting to shoot rather than being unable to.