He Turned Aura Into Electricity: Godspeed
Speed of Lightning and Whirlwind speed up different places

In Yoshihiro Togashi's HUNTER×HUNTER, Killua has a Nen ability called Godspeed (神速, kanmuru). He runs an electrical aura through his own body and raises what that body can do.

Godspeed comes in two modes, Speed of Lightning (電光石火) and Whirlwind (疾風迅雷), and the manga explains the difference between them. Those two land on two different places in the machinery of the body. That is what this article is about.

Godspeed splits in two

The explanation comes during the fight with Youpi in volume 27.

Speed of Lightning, in which he moves his body by his own will —

and Whirlwind, in which his body works automatically, responding to the opponent's movement.

Yoshihiro Togashi, HUNTER×HUNTER vol. 27, ch. 281 (Shueisha) ／ 原文「自分の意志で肉体を操作する“電光石火”と／相手の動きに感応して自動的に肉体が働く“疾風迅雷”」

An attack programmed in advance fires on the “ripple” in the aura that signals the enemy's intent to harm.

Skipping the brain's command, delivered by reflex alone, an attack that has passed beyond human limits

easily outran the movement of the enemy's body.

Same, vol. 27, ch. 281 ／ 原文「予めプログラムした攻撃が 敵の害意を示すオーラの「揺らぎ」に反応する／脳の命令を省き 反射のみで繰り出される 限界を超越した攻撃は／容易に敵の肉体の動きを追い越した」

The two speed up different places

Broadly, how fast you react is three stretches of time added together. You notice the stimulus, you decide what to do, and you move. The Japanese neuroscience reference Brain Science Dictionary splits reaction time into at least these three, and you can cut it finer than that.

The fight with the Oroso siblings

In volume 23 Killua catches a Nen fish (datsu) thrown by the Oroso siblings. Volume 27 later points back to this moment as an example of Whirlwind.

But what Killua actually said on the spot was something else.

Only the last throw — I know exactly “when” and “where” it's coming…!!

Yoshihiro Togashi, HUNTER×HUNTER vol. 23, ch. 240 (Shueisha) ／ 原文「最後の一投だけは「いつ」「どこに」投げるか完全にわかる…!!」

In other words, he had his hand set to catch, in advance, at the spot it was going to arrive.

The siblings, for their part, say this.

Catching a Nen fish? No human has reflexes faster than light!!

Same, vol. 23, ch. 240 ／ 原文「念魚を掴むなんて超光速的な反射神経 人間にあるわけねーだろ!!」

Killua had predicted the incoming attack and built the answering movement beforehand.

Whirlwind — past the brain and past the spinal cord

Tap below the knee and the leg kicks. That is the patellar reflex, a tendon reflex in clinical terms. In a tendon reflex the signal never reaches the brain; it turns around in the spinal cord, so no time is spent deciding. Pulling your hand back from something hot is the same kind of spinal reflex, and the Brain Science Dictionary describes it as something that “happens in a short time, requiring no cognition or judgement.”

Real reflexes run 25–50 ms. An ordinary reaction — perceive with the senses, decide, then move — runs 150–300 ms. A whole order of magnitude apart.

The explanation of that scene has a second half, and it is about the route itself.

Rather than carrying an electrical command from the skin's touch receptors to the brain, and from the brain to the nerves of the hand, at the moment the Nen fish touched his forehead —

he had used Nen to arrange it so that the instant his aura sensed the Nen fish, the signal “grab” would go straight to the nerves of his left hand!!

Same, vol. 23, ch. 240 ／ 原文「念魚が額に触れた時 皮膚の触覚から脳へ 脳から手の神経へと 電気指令を伝えるのではなく／オーラが念魚を感知した瞬間 直接左手の神経に「掴め」という電気信号を送るように念で操作しておいたのだ!!」

Here is the real route. A signal picked up by the skin travels up the dorsal column of the spinal cord to the brain, and the command the brain issues travels back down the spinal cord to the nerves of the hand. Out and back, both legs pass through the cord. What Whirlwind uses instead is this: the moment the Nen fish reaches the skin, the aura beside the hand fires and sends an electrical signal straight into the nerves of the left hand. A tendon reflex does not reach the brain, but it does reach the spinal cord and turn around there. Whirlwind does not pass through the cord either.

In volume 27, what Whirlwind senses is the “ripple” in the aura. That is not an input real nerves use, so the same numbers do not transfer — but because it skips the human sense organs, below 25 ms is on the table.

To get a feel for the order of magnitude, put a handgun round next to it.

A 9×19mm Parabellum round (9mm Para) travels at roughly 360 m/s in a standard load. Fired from 10 metres away, it arrives in 28 ms. At an ordinary reaction of 150–300 ms the round lands before you start moving; a tendon reflex at 25–50 ms is the first thing in the same order of magnitude.

If the Oroso siblings' Nen fish moved about that fast, you start to see how fast this Nen-driven reaction has to be. To stop it after it touches his forehead, he has to close his hand while it advances 1 mm. That is 0.003 ms of usable time — about one nine-thousandth of a 25 ms tendon reflex. The manga never states the Nen fish's speed, but since it is drawn as caught and stopped, Killua's hand moved at a speed to match.

What Whirlwind does is redraw the path the signal takes. The most interesting thing about this ability, to me, is that it offers a way past a human limit rather than a way to push against it.

Redrawing a path means deciding in advance what will run along it. That is why Whirlwind is described as “an attack programmed in advance.” The speed comes out as a result of what was set up beforehand.

Same Whirlwind, different trigger

Put the two scenes side by side and the trigger is different.

In the Oroso fight in volume 23, what it responds to is the Nen fish itself arriving at his forehead. Contact is the starting point, so it cannot fire any earlier than that. The Whirlwind used against Youpi in volume 27 responds to “the ‘ripple’ in the aura that signals the enemy's intent to harm.” Intent can be sensed before the attack lands, so it can fire earlier than contact.

Volume 27 points back at the dart-stopping movement in volume 23 and says it “is precisely the latter,” filing it under Whirlwind after the fact. The mechanism is the same; only what sits in the trigger differs. Which means Killua is choosing what to make it respond to, and building that in.

In the volume 23 scene, Killua had read “when” and “where” the Nen fish would come. If you know where it will arrive, putting your hand there and using contact as the trigger is the surer option. Against Youpi, where neither the place nor the timing can be read, a ripple is the only trigger available.

From here on this is speculation. If he had already programmed the ripple-reading version back in volume 23, he might have responded to the aura's movement before the Nen fish appeared and caught it earlier than the skin-contact condition allows. Or he might have been too early, closing his hand on a fish that had not arrived yet.

In the Youpi fight there is no telling where the enemy's intent will come from. That needs a program watching a wide area. In the Oroso fight the arrival point is fixed at his forehead, so whether he watches for a ripple or waits for contact, the forehead is all he has to watch. If a more complicated Nen program costs more aura, then a scene he has read completely costs him less.

If contact is a good enough starting point, the defending side has the same road open. In volume 9, when word arrives that the Nen user Dalzollene may have been killed, boss Nostrade is astonished: “I don't believe it — the man's a Nen user,” “he should be conditioned well enough to take ten rounds and be fine.” He is surprised on the assumption that a Nen user can absorb that much. And if the arrival point is fixed at the forehead, there is also the option of gathering aura there before contact. Gyo, which Biscuit explains in volume 15, is the technique of shifting the distribution of aura to adjust attack and defence to the situation. Raise the forehead's attack-and-defence value and he might have taken the hit without catching anything. For the last throw he knows “when” and “where” it is coming, so he could even go to Ko, gathering the aura of the whole body into a single point. Ko puts the gathered spot at 100 and everything else at 0 — but he could take the earlier attacks without it and gather at the forehead only for the last throw, whose arrival he has read, and he might well have blocked it.

Even so, Killua chose to catch and stop it. The program he built for this fight is the first instance of the movement later called Whirlwind. In that sense the Oroso siblings are the opponents of the fight in which Killua's ability took shape.

Is Speed of Lightning really Transmutation?

Whirlwind has taken us this far; from here it is Speed of Lightning. For a moment I was unsure which Nen category it belongs to. The manga says he “operates his body by his own will.” Operating yourself is something the manga presents as a Manipulation move. The principle that “Manipulation abilities are first come, first served” appears first in volume 22 and is repeated in volume 37; volume 37 adds that if you manipulate yourself first when you activate, you can block an enemy's Manipulation. On that reading, Godspeed's build — set something on yourself in advance — overlaps with how Manipulation thinks. In volume 31 there is a scene where Killua runs with his younger sibling Alluka in his arms, using Speed of Lightning, and pulls away from Tsubone, who has transformed into a motorcycle.

That scene is about keeping the distance open by continuing to run, not about a fast start. Where Whirlwind speeds up the start, Speed of Lightning raises the speed of the movement while it is happening.

Speed of Lightning fires by his own will, so the deciding part does go through the brain. The explanation in volume 23 is about Whirlwind, so it does not necessarily transfer, but if both are Godspeed I take it that the aura carries the delivery leg too. Nerve conduction has been measured at roughly 48–59 m/s. That is 17–21 ms to cover one metre inside the body. Since reaction time itself is 150–300 ms, the delivery is only around a tenth of it.

Which suggests Speed of Lightning's speed is not a story about delivery time. The command that moves a muscle is electrical to begin with, and the larger the force, the larger the motor units recruited, in order. In the same way that pushing more current into a motor raises both its speed and its torque, reading Speed of Lightning as acting on how hard the electricity is driven makes the pieces fit. The bigger the current, the bigger the force, and the same body moves faster.

As I said at the start, Godspeed is an ability that turns aura into electricity. Killua is a Transmuter, and on the Nen category chart the opposite of Transmutation is Manipulation — his worst position. The explanatory diagram in volume 23 says the aura beside his hand “becomes electricity through Nen manipulation and sends the command straight to the hand, so it is limitlessly fast.” Do the same thing by his own will and he can send commands straight to his legs and to the rest of his body. And if that electricity is itself the power source, he can hold the speed while he runs. That is Speed of Lightning; set a condition and let it fire automatically and that is Whirlwind. Read that way, Transmutation alone seems to account for it.

Experts read ahead, so they can wait

Back to the real world. Research on reaction time has piled up results showing that raw speed barely moves. Two years of practice does not change simple reaction time. So the interest has shifted from getting faster to reading and waiting.

There is a study of football goalkeepers. Shown footage of penalty kicks, expert keepers waited longer before initiating a response than novices. They made fewer corrective movements, and their gaze concentrated on the kicking leg, the standing leg and the ball. Novices spent longer looking at the trunk and the arms.

Reading ahead means you do not have to move in a hurry. Move early and the feint gets you. Build the movement in first, and let the ripple in the aura set it off — that is the order of operations.

Measure your own reaction time

Run both the visual mode and the audio mode and you will find out which of your eyes and ears is faster.

Summary

Rereading the ability's explanation alongside some physiology kept me entertained for longer than I expected.

If I have misread something, or you read it differently, tell me. The contact form reaches me.

Sources