Kenshi Yonezu Unveils the Creative Process of ‘Chainsaw Man’ Theme Song ‘KICK BACK’: Interview

Kenshi Yonezu‘s recently released new song, “KICK BACK,” was created as the opening theme of the TV anime series Chainsaw Man. Yonezu wrote the music and lyrics himself, and Daiki Tsuneta (King Gnu, millennium parade) joined him to work on its arrangement.

“KICK BACK” has taken the charts by storm. The song debuted at No. 1 on the Oct. 19-dated Billboard Japan Hot 100, and is creating waves around the world, having become the first song by a Japanese artist to make it into Spotify’s Top 50 Global daily song ranking.

Chainsaw Man, based on a comic by Tatsuki Fujimoto, is the story of Denji, a Devil Hunter, who enters a contract with a Chainsaw Devil that enables him to turn into “Chainsaw Man” to fight devils and Fiends. Part 1, the “Public Safety Arc,” was published in Weekly Shonen Jump starting in 2019, and Shonen Jump+ began publishing Part 2, the “School Arc,” in July 2022. The anime adaptation has drawn a great deal of interest because it was produced by MAPPA, which is also responsible for Jujutsu Kaisen, Yuri!!! on Ice, and Attack on Titan, and because the ending themes of each of its 12 episodes were written by different artists, such as Vaundy, Zutomayo, and Aimer.

In the interview below with Billboard Japan, Kenshi Yonezu discusses the creative process behind “KICK BACK.”

What was your initial response when they asked you to write the opening theme to Chainsaw Man?

Yonezu: I’d always wanted to write it. When I read the comic, I’d often think about what kind of theme I’d write for it if they made an anime adaptation. When it was actually decided that I’d be the one creating the theme for the show, I was overjoyed. I’d been thinking about what kind of song I’d write before anyone had even brought up the possibility of my actually writing it.

What do you like about Chainsaw Man?

Yonezu: In the comic, demons are constantly hurting people in grotesque ways. The world it depicts is a very serious one, but the central character, Denji, is, how should I say this…just an idiot. Denji’s presence turns this negative environment and serious story into a comedy. That makes it really fun. It’s about a guy with no education working really diligently and seriously and just making a total mess of things. I’d never seen anything like that before, and it’s just delightful.

You said that even before you were approached, you’d been thinking about what kind of music you’d create. What were your first ideas?

Yonezu: First, I wanted to go with drum and bass. There’s still a bit of that in “KICK BACK,” but during the demo stage it was crazy drums with long synth phrases, true drum and bass style.

How did you start actually going about writing the song?

Yonezu: I started by meeting the director and the people on the anime production end. I remember the director asking that I “make the song like a roller coaster.” Lots of transitions, with dramatic changes between parts, so it felt like different songs. A song with big differences between the highs and lows. He wanted a song that would fling you around, and before you knew it the song would have ended. At first, it felt like he was talking about something really difficult, but when I thought about it more, I realized that the word he used, tencho, could be used to refer to both a change of key and also to a change in the tone of the music. I didn’t know which one he was asking for, so I decided to do both.

Chainsaw Man can be looked at from all kinds of different directions. Which aspects of it did you try to express through music?

Yonezu: The thing that jumps out at you first about Chainsaw Man is its grotesqueness. Denji rips apart all kinds of things and kills devils in gory ways, and those blood-spattered depictions stand out. Since I was writing the opening theme, I thought it would be good to make a song that unfolds Chainsaw Man and provides an overview of the story.

Also, Chainsaw Man‘s story is one of betrayal after betrayal, and at the heart of this story you have this complete idiot, Denji. It constantly skates the line, teetering on the edge of completely breaking down with this really pop sensibility. It’s a really thrilling comic, so I thought it might be great to express that feel in the music. 

“KICK BACK” has a line, “Doryoku, Mirai, A Beautiful Star” (“Hard Work, Future, A Beautiful Star”) that’s from the Morning Musume. Song, “So Da! We’re ALIVE.” What gave you that idea?

Yonezu: Pure intuition. I don’t know why, but I just wanted to do it. I had my heart set on using that line no matter what.

The song came out in the year 2000. Did you listen to it back when it was new?

Yonezu: Yes. It was the music of my generation, so I listened to it a lot when I was in elementary school. During the chorus of “So Da! We’re ALIVE,” they sing “Shiawase ni naritai” (“I want to be happy”). The way they sing it is like “Shi—yawase.” That really jumped out at me when I was a kid. Instead of pronouncing it “shiawase,” they pronounced it “shiyawase.” Sometimes when my friends and I were playing, we’d just sing that part at each other, and it really made a strong impression. When I started working on the opening theme to Chainsaw Man, I remembered that. Once those two things connected, the rest flowed faster. I listened to the Morning Musume. song again and I was like “It’s gotta be this.” If I was going to write the opening theme for Chainsaw Man, I had to sample this, there were no two ways about it.

The chorus has lyrics like “fill it up with happiness” and “fill it up with luck.” Would you say that “happiness” is a key word?

Yonezu: Denji was born in just dire circumstances, and I think when people are confronted with that kind of misfortune, they stop thinking about specifics. It’s more like “I just want to be happy.” They don’t think as far as “Well then, what should I do to become happy?”  That’s why I felt I needed to go with simple words like “happiness” and “luck.”

You and Daiki Tsuneta worked together on the arrangement of the song. You two have long been close friends, but what led you to working on this song together?

Yonezu: Once, when Daiki and I were drinking together, we got to talking about Chainsaw Man, and we were like “It’s awesome! What a great comic!” One day, after they approached me to write the opening theme, I went drinking with Daiki again, and I said, “Hey, come to think of it, I’m doing the music for Chainsaw Man. Do you want to do it together?” It was a really casual process that lead to the collaboration.

What essence did Tsuneta add to the song?

Yonezu: I was really impressed with him yet again. My demo took a stoic drum and bass approach, but he gave it an extra boost by adding a rough, hoodlum-like feel.

KICK BACK is already creating quite a stir in Japan and overseas. What are your feelings on reactions to it, including its activity in the charts?

Yonezu: I’m happy to see it. Above all else, I think Chainsaw Man is wonderful. The opening animation, especially — I’d say it’s the best of any anime I’ve ever seen.

I’m sure that there are people overseas who’ve learned the name “Kenshi Yonezu” thanks to this. You, as an artist, have been highly influenced by young adult comic and animation culture. I think one of the notable features about modern Japanese pop culture is having musicians like you writing the theme songs for anime. What do you think you’ve taken from young adult comic and animation culture? What aspects of that culture do you carry on in yourself and your work?

Yonezu: I’d originally wanted to be a comic creator. It’s not so much a case of comics influencing a musician as someone who wanted to be a comic artist but ended up being a musician instead. So, inside me, I still have that child, that pre-teen, that wanted to be a comic creator. I drew comics since I was little, but then I switched to music, so I’ve never really experienced failure in my comic aspirations. If I’d really tried to become a comic creator, I’d have had all kinds of different experiences. Maybe I’d have brought my creations in to an editor, who would point out problems and issues, and I’d think, “I guess I just don’t have any talent when it comes to comics.” But I’ve never experienced that, so there’s still a part of me that thinks that maybe I am a comic creator — that maybe I’d be better at comics than at music. I don’t feel like a musician that was influenced by comics, but more like someone who has kept writing music as if he were writing comics. So the two are tied up really tightly together.

You drew the Chainsaw Man illustration on the artwork of the single. What meaning or ideas went into it?

Yonezu: The first version had three figures on it — Denji, Aki Hayakawa, and Power. But when I looked at the finished version, I thought, “No, that’s not right.” So then I decided to go with a movie poster-like visual, which is what led to the final jacket illustration. The composition, with the arm, was influenced by the poster for Parasite. On the Parasite poster, there are these legs jutting into the poster from the side. I like the disturbing feel that creates. When I applied that sense of disquiet, that cool tone, and that feeling of miserableness to Chainsaw Man, the jacket illustration is what came out.

What are your feelings on the style Tatsuki Fujimoto uses in Chainsaw Man?

Yonezu: There are elements of the story that really evoke sympathy. Partly because we’re around the same age, I feel like we’ve seen similar things in our lives. He has an amazing imagination, and the artistic ability to bring it all to life. He creates things that only he could. I think he’s a rare genius.

–This interview Tomonori Shiba first appeared on Billboard Japan.

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