Ninomiya is highly skilled in shooting and fighting in general, as is testified by him being the No. 1 Shooter and No. 2 overall combatant in Border, as well as the captain of the B-Rank #1 (formerly A-Rank) unit. His proficiency extends to strategy as well, making him an effective leader. In rank wars, he generally fights on his own, as his individual power is great enough to crush most opponents. Due to his offense and defense in both close and mid-range having no openings, he can take on Attackers on his own. He was able to single-handedly defeat Kuga, a fighter on par with some A-Class agents. In spite of his overwhelming strength, he is very alert in battle, and can switch from attack to defense in an instant.
As a Shooter, Ninomiya adopts a peculiar fighting style. He is the only Shooter so far capable of manifesting trion cubes without needing to use his hands, which he keeps inside his pockets. He also has the singular ability to shoot bullets seemingly without needing to summon a trion cube, just by pointing his finger at the target, which he most likely accomplishes by summoning, dividing and firing the cube at extreme speed. The efficacy of this tactic lies in that the opponent will not expect an attack, and thus will not be prepared to defend. Unlike Izumi, he does not use Full Attack in open confrontations, which enables him to put up a Shield more swiftly to cope with sudden attacks; his enormous amount of trion makes the decrease in offensive power relatively insignificant. He is able to create composite bullets rather quickly, or at least fast enough not to need to take cover while merging trion cubes. After obtaining the title of No. 1 Shooter, he further polished his technique under Izumi's guidance.
Ninomiya had the greatest trion capacity in all of Border before Chika's arrival, This causes his trion cubes to be bigger than even Izumi's. He can shoot extremely powerful Asteroid bullets several times and fire a continuous Hound barrage without any sign of overusing his trion.
As the Shooter with the highest score with this Trigger, and the agent with the second highest score with any Trigger, Ninomiya is extremely proficient with Asteroid. Thanks to his abundance of trion, a single volley is powerful enough to break the Shield of a former A-Rank agent and damage their body, as well as to destroy small structures. He scatters his bullets evenly around him, targeting an area that is larger than the opponent, but not so much that too many shots will miss the target. Due to Ninomiya dividing the trion cube in 6 or 16 parts, his bullets are shaped like pyramids.
Due to his extremely vast amount of trion, Ninomiya's Shield is much more durable than the norm. He can block an Eaglet with a Shield about twice as large as the focused Shield of other agents. With two of them, he can even stop an Ibis completely. In rank wars, he occasionally casts a Shield to protect an opponent in order to defeat them himself.
At mid-range, Ninomiya uses the chasing bullets to pull the opponent closer and finish them off with a sudden volley of Asteroid. However, he can use a long-ranged, continuous Full Attack Hound to bombard a large area from afar, wearing down the defenses of any opponent within range and gradually destroying their trion body.
Ninomiya's Gimlet is powerful that it can break through the combined shields of four Idras and damaged them directly. This is all the more impressive considering that those shields were able to withstand the combined fire of three Eaglets multiple times without a crack.