"Wanting to Know What Cannot Be Known" — How Yorushika's "Aporia" Captures the Soul of Chi.

The ending theme for Chi. — About the Movement of the Earth is "Aporia" by Yorushika, written and composed by n-buna, who is himself a fan of the original manga. The song was written specifically for the anime.

Read the lyrics:

• [Yorushika Official Site](https://yorushika.com/lyrics/detail/68/)
• [Uta-Net](https://www.uta-net.com/song/361382/)
• [UtaTen (with furigana)](https://utaten.com/lyric/mi24092531/)

What "Aporia" Actually Means

Aporia is a term from ancient Greek philosophy. It describes the state of being genuinely stuck — facing a problem with no apparent solution, or experiencing deep puzzlement about something you cannot resolve. The feeling of being at an intellectual dead end, knowing you don't know, and not knowing how to get out.

Socrates used aporia deliberately in his dialogues. By leading his conversation partners into aporia — into the uncomfortable realization that they didn't actually understand what they thought they understood — he created the conditions for genuine inquiry. Aporia wasn't the failure state. It was the starting point.

n-buna described his intent for the song in a comment:

"I wrote about the desire to know things that cannot be known, likening it to aporia. The balloon in the lyrics is a metaphor for the unlimited desire for knowledge."

One sentence. That's everything you need.

The Paradox at the Center

The word aporia points to a contradiction: pursuing an answer when you don't know if an answer exists, or when reaching the answer might cost you everything.

The song opens with a quiet image of this:

*描き始めたあなたは小さくため息をした*

"You who have begun to draw let out a small sigh" (Lyrics: n-buna / Yorushika "Aporia")

Beginning to draw — beginning to seek — already brings a sigh. Not defeat. The sigh of someone who has taken on something difficult, knowingly.

This is exactly where the characters in Chi. live. They know that believing the earth moves around the sun is dangerous — possibly fatal. They know the knowledge may not survive them. They know they may die without vindication. And they cannot stop.

The desire isn't instrumental. It isn't "if I find the answer, I'll be rewarded." It's closer to: "I need to know because I need to know." Logic can't reach it. The impulse is prior to reason.

That state — wanting to know what you cannot, and perhaps should not, know — is aporia in motion.

The Balloon

The specific image n-buna chose for "unlimited desire for knowledge" is a balloon. It appears twice in the lyrics, each time carrying the same characters forward:

*長い夢を見た、僕らは気球にいた*

"I had a long dream — we were in a balloon" (Lyrics: n-buna / Yorushika "Aporia")

*広い地平を見た、僕らの気球は行く*

"I saw the wide horizon — our balloon goes on" (Lyrics: n-buna / Yorushika "Aporia")

A balloon has no fixed destination. It rises. That's its nature. The higher it goes, the more sky appears above it. There is no ceiling to reach, no moment of arrival. The rising is the point.

And the song ends — not with arrival, but with reaching:

*水平線の先を僕らは知ろうとする*

"We try to know what lies beyond the horizon" (Lyrics: n-buna / Yorushika "Aporia")

"Try to know" — not "know." Not "have found." The attempt itself is the subject of the song.

In Chi., the pursuit of heliocentrism passes from person to person across generations. One scholar dies, another picks up where they left off. The goal isn't "we will reach the summit." The goal is the ascent itself — the knowledge-seeking that doesn't end because one person's life does.

The balloon doesn't fall. The desire doesn't stop. Even when the people carrying it die, something keeps rising.

The Value of Not Knowing That You Don't Know

The philosophical point of aporia isn't just that you're stuck. It's that recognizing you're stuck is itself a form of knowledge — and a necessary one.

There's a difference between not knowing something and not knowing that you don't know it. The first is a starting condition. The second is the obstacle. Aporia forces you to confront the second honestly.

The characters in Chi. move through this honestly. They confront the question: is this thing I believe — the earth moves — actually something I *know*? Or something I want to believe? The willingness to sit with that uncertainty, rather than retreating into either comfortable faith or comfortable denial, is what the song is really about.

Why This Song Works as an Ending Theme

An ending theme plays at the end of every episode. Whatever has just happened — a death, a discovery, a betrayal, a moment of recognition — the song arrives to close it.

"Aporia" is right for this role because it doesn't resolve anything. It sits in the middle of the question. Every episode of Chi. ends in the middle of something: knowledge that hasn't been confirmed, people who haven't survived, a relay race still in progress. The song matches that feeling exactly — not triumphant, not defeated, but reaching.

"I don't know. But I keep going."

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Vocabulary:

• Aporia: From Greek *a-* (without) + *poros* (passage). A problem with no clear solution; the philosophical state of genuine puzzlement
• Yorushika: Japanese music unit consisting of n-buna (composer/lyricist) and suis (vocalist)
• Ending theme: The song that plays at the close of each anime episode, usually over the credits