|“||Slinking off to lick our wounds doesn't sit well with me. If we gotta bail out, I wanna do it in a blaze of glory... Well, that's what I'd normally say...||”|
Koarai is a light-skinned boy of average build. He has slit pupils and short-to-medium dark blonde hair that is slicked into an upturned point in the front. He seems to favor wearing light, dark-colored jackets, although he has also been seen donning hoodies.
In his trion body he wears a navy blue, long-sleeved jacket with black lines bordering the zipper and the high collar, which he keeps open, and running horizontally around it both on the inside and the outside. Vertical black stripes run from the collar to the wrists of the jacket, interrupted only where Border's logo is emblazoned on the outer side of each sleeve a little below the wearer's shoulders. On the right breast are two piped patch pockets closed by flaps, bigger than the ones that can be found in the vicinity of his left hip, while on the left is the B-rank logo. Underneath the jacket is a black shirt with a round neck. The uniform is completed by dark gray boots and headphones and a pair of black pants.
Koarai is high-spirited and easily excitable, and wears his heart on his sleeve. He has a competitive side, which is most visible when he discusses strategy with Okudera in front of their captain and when he fights in rank battles as well as when he cheers for others. Nonetheless, he shows no hints of resentment when he loses, instead congratulating the winner with enthusiasm and admiring more skilled Attackers. He can be defensive about his own abilities, although he is willing to recognize his shortcomings for the good of the team. He can act a little smug when things go his way.
Koarai has a well-deserved reputation for being reckless in combat, attacking a Rabbit on his own after it pounced on Okudera against his captain's advice and preferring to fight to the last even when retreating is the best move. However, he was recently noted to have grown more prudent, even though agreeing to retreat left him feeling dejected. In the planning phase of rank battles he has occasionally exhibited a penchant for suggesting courses of action based purely on how entertaining they had the potential to be. It is possible that this tendency of his has also subsided, as in round eight Azuma Unit chose Exhibition Hall, a map where Azuma is known to excel.
Koarai and Okudera are teammates who seem to enjoy a good relationship and a friendly rivalry when discussing strategy in front of Azuma. Due to their differing personalities, Okudera may end up Koarai's more reckless tendencies, and may feel frustrated when Koarai acts smug around him. This however does not diminish the concern Koarai shows for Okudera in combat, and the latter has also demonstrated to care about Koarai's mood. They address each other by surname, without honorifics.
Azuma is Koarai's captain and mentor. He educates him in strategy while giving him the space to come up with his own plans. In addition, he is to an extent responsible for Koarai's Trigger Set, having forbidden him to equip Sub Triggers until he showed to have grown enough. Koarai greatly respects Azuma and is filled with pride when validated by him. His admiration dates to before he joined Azuma Unit, as he clung to the captain's leg and begged for the chance to be part of it. They address each other by surname, with Koarai adding the honorific -san.
Hitomi is a big sister figure to Koarai and Okudera, who joined Border when she did, and she may invite them to cool down when their discussions turn into ego battles. He has grown accustomed to finding her giggling while watching horror movies in the dark in the strategy room. Koarai calls her by name, to which he appends the honorific -san, while she uses his nickname without honorifics.
Koarai and Satori are school friends.
Koarai and Ikoma are presumably on good terms, with Koarai feeling entitled to bemoan Ikoma's involuntary foul when he sparred with Hyuse. Koarai addresses Ikoma by shortening his surname and appending the honorific -san, while Ikoma uses Koarai's nickname and no honorifics.
Koarai and Murakami might be close, since the former referred to the latter by his first name, albeit with the addition of the honorific -san.
Koarai is presumably somewhat close with Tsuji, taunting him when they clashed in round four. For his part, Tsuji appears not to mind Koarai's informality. Nonetheless, Koarai acknowledges Tsuji's superior swordsmanship and addresses him respectfully, using his surname and the honorific -senpai.
Inukai knows Koarai well enough to be able to tell that he would generally prefer to hope in a final shot rather than retreat, as well as to call him by his nickname without adding an honorific.
Arashiyama knows Koarai well enough to be able to tell that he would generally prefer to hope in a final shot rather than retreat.
Koarai and Miura know each other at least by sight, although Miura's popularity among younger Attackers could imply that they are closer than that. Koarai addresses him by his surname followed by the honorific -senpai, suggesting respect.
Koarai was deeply impressed with Hyuse's combat prowess. Though losing all five rounds to him and subsequently rooting for his opponents, he later enthusiastically greeted and complimented the recruit, going so far as to invite him to join Azuma Unit.
- (Azuma's motto, taken up by Koarai and Okudera) "When you fight with strategy, take into account the enemy's strategic prowess."
- (To Haruaki Azuma) "I really think we should tweak the map. It would be super fun."
- (To Tsuneyuki Okudera) "I'm sure we'll get more ideas if it's more fun."
- (To his teammates) "Slinking off to lick our wounds doesn't sit well with me. If we gotta bail out, I wanna do it in a blaze of glory... Well, that's what I'd normally say..."
- "They think I've grown? That's nice and all. But all I could actually do in the end was run away..."
- "Noboru (登?) means "rise, mount, board, climb", while "Koarai" (小荒井?) means "small wasteland pit".
- He likes soccer and karaage fried chicken.
- Despite Koarai and Okudera using Grasshopper in both rank battles in which they appeared, as well as it being included in their Trigger Sets in Border Briefing File, it is in fact a Trigger which they add only before certain matches.