William Gleason prepares to enter a match with student Joshua Puskarich at his Shobu Aikido studio in Somerville. (Photo: Amine Trabelsi)

In cities notable for pop culture geekery and technological nerdery, it might not be known a superstar in the world of aikido is among us: William Gleason, 71, a seventh-degree black belt who began studying the martial art in 1970 at the world headquarters in Japan, is a twice-published author on the topic and runs five studios from the Midwest to Somerville.

Gleason will be giving a demonstration of aikido Thursday, taking questions and offering beer, sake, and snacks to start off a week of free beginner classes for anyone 15 and up.

While the concept of “celebrity” probably doesn’t fly in a martial art whose name translates as “the way of harmonious spirit” or “the way of unifying life energy,” Gleason is the real deal.

Not many westerners have so high a rank in aikido, or as high a sense of mission when it comes to giving practitioners a sense of the solemnity of the art.

“Unfortunately, Aikido today has lost its origin,” he told interviewer Pasquale Robustini. “Aikido was once a formidable martial art, yet today it receives little respect as a self-defense art from serious martial artists of other disciplines.”

That means people signing on at his nonprofit Shobu Aikido in Somerville won’t just learn to fight, but will get the spiritual underpinnings as well – the unified “Aiki” that underlies the physical and makes the self-defense part possible. The studio’s definition:

Aikido is a martial art without competition. The harmonious and natural structure of aikido allows full contact and full speed training with very little risk of injury. The art of aikido unifies offense and defense and teaches the art of remaining neutral and balanced between the two.  Based on the battlefield martial arts of Japan, aikido utilizes all methods of barehanded training as well as short staff and sword.

The short, free demonstration is at 8 p.m. Thursday at Shobu Aikido, 34 Allen St., near Union Square, Somerville. Doors are at 7:30 p.m.