Everything Starts With a Con Man at Heavens Arena
Taught by Wing, Episodes 27–44
Why Wing Teaches Them At All
Gon and Killua don't seek Nen training out of curiosity. They get wrecked at Heavens Arena by fighters who are clearly operating on a different plane entirely, and Wing, a con artist with real skill hiding behind a sales pitch, is the one who finally tells them the plane has a name. Everything this page covers happens because two overconfident kids got humbled first.
Ten
The baseline. Wrapping your own aura around your body to hold it in instead of leaking it constantly, which every living person does without knowing it. Ten alone won't win a fight, but skipping it means an opponent with any Nen training can read you, injure you, and drain you faster than you'd ever expect from someone who hasn't learned anything flashy yet. This is the "put your seatbelt on" of the entire system.
Zetsu
The inverse of Ten: suppress your aura completely instead of holding it in. Makes you invisible to other Nen users and to Nen-based detection, at the cost of losing your own defenses in the process. Killua uses this instinctively long before anyone teaches him the name for it, which tells you everything about what his childhood actually trained him for.
Ren
Push past Ten's baseline and flood your aura outward on purpose. This is where a Nen user actually becomes visibly dangerous, more power available for a strike, but also more energy spent and more obvious to anyone else nearby who can sense it. Ren is offense. It is also a warning shot whether you mean it as one or not.
Hatsu
The one Wing won't hand you a formula for
Everything before this point is technique anyone can learn with enough repetition. Hatsu is different: your own personal application of Nen, built out of who you actually are rather than copied off a teacher. Wing is explicit about this in the Heavens Arena scene where he introduces it, Nen abilities are shaped by nature and nurture both, which is why no two users ever end up with the same move even when they share a type.