At five years old, Tenshin Nasukawa was enrolled in karate class alongside his mother, father and siblings.

It wasn't supposed to lead anywhere in particular. The plan, according to Tenshin's father, Hiroyuki, was simply to impart the spiritual and psychological benefits of the martial arts—honor, discipline, respect, focus—into his son at a young age. 

In the early 2000s, however, the martial arts in Japan weren't just black belts and horse stances. K-1 Kickboxing and Pride FC were combat sports powerhouses. The two promotions were turning heads overseas while packing tens of thousands of fans at home into arenas with events built around almost literal giants. 

It was a spectacle unlike anything else, and it was a spectacle that inspired Tenshin to seek in-ring stardom.

"I practiced karate until I was in sixth grade. I was winning competitions at a national level, but at the same time, there were the big shows like K-1 and Pride," he told Bleacher Report through a translator in an exclusive interview. "I wanted to participate on that big stage...there was no specific individual that inspired me. I was attracted to the stage."

Fourteen years removed from those first karate lessons, Nasukawa's childhood dream has come true. He already owns a trophy mantel stocked with medals, awards and title belts. He is the face of a major promotion in Rizin FF. He has already stolen shows in some of Japan's most iconic sports venues.

And he did all that before graduating high school.

Nineteen years old, 25-0 in professional kickboxing, 4-0 in MMA and looking toward one of the most important fights of his career, the young stud opened up to Bleacher Report about his rise to the top and where he goes from here.

Youth karate and professional kickboxing are two very different things, but the training he did then has a number of similarities to what he does now. 

Just across the border of Tokyo prefecture lies the sleepy bedroom town of Matsudo. Across the street from a tiny cafe and sitting above a realtor's office is the shiny new Teppen Gym, where Nasukawa does the bulk of his training. For the most part, it resembles a standard training center, stocked with heavy bags, a ring and a large collection of exercise equipment.

The little details, however, show that this isn't just a gym...six days a week, it's his home. 

Greeting people at the door is a life-size statue of Kenshiro, lead character from the classic anime Fist of the North Star, and Nasukawa's mother, who works as the gym's receptionist. Nearby, his father watches him do his morning warm-ups. It's a unique, cozy vibe, but a fitting one for him.

Despite his stardom, at 19 years old Nasukawa's personal, professional and family lives are still tightly intertwined. According to Hiroyuki, that's exactly how Tenshin wants it. While this is all still something of a surprise, he is proud to play a continued part in his son's success.

"I used to practice karate, but I was never a fighter myself," he said. "Tenshin kind of made me into a trainer and as I was supporting his dreams, his dreams turned into my dreams...with all the momentum going right now, I believe I need to support my family in this industry."

Once again, though, this wasn't really a plan for Hiroyuki. While he wholly supported Nasukawa's moves from traditional karate to full-contact karate to professional fighting, the risks aren't lost on him.

Answers to questions about what it's like to see his son compete are considerably more contemplative and somber. Ultimately, he acknowledges there are worries, but his son's drive and success to this point mean he would rather help than hinder.

"There are definitely concerns. For sure there are concerns about watching him fight," he said. "But right now, he's starting to make a name for himself...and I want my son to shine and be the best that he can be at this time."

In the era of LaVar Ball, it's easy to question whether a recipe for success can withstand a heaping helping of family involvement. Even with outside managers and coaches around him, having both parents looking over his shoulders as he works (and a soon-to-debut sister sharing the same mats) might be overwhelming as he continues to develop.

Tenshin, though, doesn't just like it. Even more than his own skills, he credits having his family around for every step of his journey as a big reason for his success to this point.

"I believe I have good responses to opponents and good reactions," he says. "But it all comes down to how I have a great environment. That itself probably makes me better than the fighters I face.

Of course, Nasukawa's environment isn't simply limited to the gym. 

Until March, he had the daunting task of juggling MMA, kickboxing and high school at the same time. That was made even more difficult by a remarkably hectic competitive schedule, which saw him compete a whopping nine times in 2017 (twice in MMA, seven times in kickboxing).

Some relief over the years came in the form of an extended curriculum, which traded shorter school days days for an extra year of classes, but it was still a tightrope walk. And it's one that he's not especially interested in restarting by enrolling in university.

"I'm super happy I don't have to go to school," he said with a laugh. "It's a big relief...I had thoughts about going to college before graduating high school, but when you think about it, you can go to college any time. Right now is not the time to be studying. I'm 100 percent focused on training right now."

With his textbooks shelved, he finds himself with a bit more down time than he used to. He spends it exactly as one would expect from a 19-year-old: playing Monster Hunter Stories on his cell phone, watching TV or hanging out with friends. For the most part, though, more time out of class means more time to spend in the gym, and that's a scary proposition for Nasukawa's opponents.

Without context, Nasukawa isn't an intimidating figure. A baby-faced flyweight, he doesn't really look the part of a ferocious fighter. Out on the streets, he doesn't have the edgy swagger one would expect from a professional face-mangler.

Anyone who has seen him in action, however, knows how scary he truly can be.

The Japanese fight scene got its first taste of Nasukawa in 2012, when the then-13-year-old began appearing on the amateur kickboxing circuit. Right from the get-go, it was clear he was an extraordinary talent, demonstrating smoothness, accuracy and power well beyond his years. 

"You could see the signs of a young star early," said War Room MMA and Kickboxing coach Steven Wright. "He not only won his amateur bouts, but he styled on guys. He could beat you with clean kickboxing scores or take something he saw in a movie and perform it to perfection against an opponent."

At 15 years old, he made the jump to the pros. Despite spending most of his life to that point throwing punches and kicks, Nasukawa remembers the gravity of the moment weighed heavily on him. 

"Before my first fight, I was a nervous wreck. While warming up, I couldn't hit pads correctly, my timing was off, I couldn't shadow box or move well. I remember thinking I was in no condition to fight," he said. "But when I got in the ring, I became relaxed. It was then I figured out that I'm good once the lights go on."

He overcame those nerves, won via first-round knockout and kicked off what has been a fearsome four-year run. Now 25-0 in kickboxing and 4-0 in MMA, Nasukawa is well established as one of the most intriguing talents in combat sports and is widely pegged as a potentially transcendent talent.

"He has fantastic speed and power. He is a great technician with excellent feints and strike selection, especially when he starts smelling blood. Add to that his more unorthodox strikes and you've got one of the best offensive palettes in kickboxing," wrote kickboxing analyst Lucas Bourdon of Au Bord Du Ring. "In terms of accomplishments, he beat four former Muay Thai stadiums champions...that's a feat very, very few foreigners can claim, and he did it before his 20th birthday...in short, he's on track to be one of the best kickboxers Japan ever produced."

In addition to the undefeated record and strong X's and O's, Nasukawa has everything a promoter could want in terms of marketability.

His high-flying style and pure athleticism are naturally entertaining, and his sheer knockout power makes him one of the few fighters you just can't look away from. On top of that is a distinctly youthful look complemented by natural showmanship. 

He has everything he needs to be a superstar. The only question is when that international breakthrough will occur. 

Few people know what they truly want in life or from their careers, regardless of their age. It's no surprise that at 19, Nasukawa isn't really sure what his endgame is, either. There is one "big-picture" goal he would like to achieve before he hangs up his gloves, though.

He wants to help return Japanese combat sports to where they were when he was growing up.

In the late 1990s and early 2000s, Japan's Pride FC was the world's biggest MMA promotion, K-1 dominated kickboxing and a slew of pro wrestling companies enjoyed simultaneous success. It was a golden age, but, one by one, calamity struck each company and eventually left the fight scene rudderless. 

Over the last few years, things have turned around. Boxing in the country has picked up steam with the success of Naoya Inoue and Ryota Murata. Interest in New Japan Pro Wrestling has spiked following the coronation of Kazuchika Okada as the promotion's leading act. 

MMA and kickboxing are both ticking upwards as well, but they lack a singular top star—a void Nasukawa is looking to fill. 

"All that I can think about right now is to become the winner of a big fight that not only all Japanese fans want to see, but all international fans want to see," he said. "The winner of big dream fights that all people want to see."

As one of the leading acts of Rizin FF, a Japanese company that promotes MMA and kickboxing, he's well positioned to make noise on both ends of the Pacific. He has the opportunity to raise his profile even further this weekend; he faces Yusaku Nakamura in the Rizin FF 10 co-main event, which takes place Sunday morning on Fite.TV.

Despite being heavily favored, Nasukawa says Nakamura still poses an interesting challenge for him.

"He blitzes in from a distance, and I've never faced anyone with that style," he said. "I know that I have a lot to learn from it, it will definitely be a new experience on my end."

It should make for an entertaining bout and should allow new areas of Nasukawa's game to shine. In all likelihood, though, it should make for another addition to his ever-expanding highlight reel.