“What was the cause of the breakup?” a radio host asks X Japan songwriter and drummer Yoshiki, early in Stephen Kijak’s new documentary We Are X. “Were you not getting along, or were there changes in the musical climate in Japan?” Yoshiki replies, simply, “My vocalist got brainwashed.”

It’s the kind of jab Keith Richards might take at Mick Jagger, or Liam Gallagher at his brother Noel—an absurd exaggeration meant to deflect blame for intra-band strife onto the preferred sparring partner of the member most prone to public complaining. But the quiet sadness with which Yoshiki responds to the question about his since-reunited Japanese metal band’s 1997 breakup is the first sign that he’s not embellishing anything. Later, Kijak fills in the true story of the decade that X’s singer, Toshi, spent in a cult that bullied him into believing the band’s music was evil.

We Are X is full of incredible anecdotes like this. They sound like tall tales of rock‘n’roll tragedy, but each one turns out to have happened exactly as described. Taken together, they create the impression that the band’s epic, three-decade history is the product of fate more than calculated myth-making. It seems obvious that the members of X Japan would have led spectacle-laden musical lives even if they’d never graduated from tiny clubs to stadiums—and this is precisely what makes their career an ideal case study in rock as raison d'être.

The band’s biography would already be familiar to American audiences if the West paid as much attention to Japanese popular music as Japan famously devotes to ours. In the 34 years since Yoshiki and Toshi formed X as high school students, their combination of KISS-style theatrics, speed-metal intensity, and emotional pop balladry has sold 30 million records. They are pioneers of a genre called “visual kei,” a Japanese glam analog born in the mid-’80s that originally paired outrageous, androgynous costumes and over-the-top performances with heavy rock music, but has since become more of a look than a sound. One critic Kijak interviews insists that the timeline of rock in Japan can be divided into two eras: “before X” and “after X.”

As We Are X tells it, the band’s story hinges on Yoshiki’s lifelong battle with illness and mortality. Kijak’s earlier documentaries about Scott Walker and Jaco reveal an ongoing fascination with one-of-a-kind musical geniuses, and X’s leader is as remarkable a subject as the director has ever profiled. A self-consciously messianic figure who occasionally poses wearing a crown of thorns, Yoshiki suffers for his art in the most literal way possible.