How to Use 「約束を守る」: Natural Japanese Verbs Used with 約束

It is Saturday afternoon at a café near the station.

Kenta is sitting by the window, checking the time on his phone.

A few minutes before 3:00 p.m., his friend Maria walks into the café.

「早いね。三時ちょうどに来ればよかったのに」

“You’re early. You could have come right at three.”

Maria smiles.

「だって、三時に会うって約束したでしょう。約束は守らないと」

“But we promised to meet at three, right? You have to keep your promises.”

Maria has not done anything extraordinary.

She simply came to the agreed place at the agreed time.

Yet this is exactly the kind of situation where Japanese uses:

「約束を守る」
yakusoku o mamoru / to keep a promise

Why do we use 「守る」 here?

And how is it different from expressions such as 「約束をする」, 「約束を果たす」, and 「約束を破る」?

Focus on 「約束を守る」

Kenta and Maria had already decided to meet at three.

In other words, the promise already existed.

Maria is not making a new promise at the café.

She is doing what she previously said she would do.

That is why Japanese uses:

「約束を守る」
yakusoku o mamoru / to keep a promise

When learners first meet the verb 「守る」, they often associate it with protecting someone or something.

For example:

「子どもを守る」
kodomo o mamoru / to protect a child

「国を守る」
kuni o mamoru / to defend a country

「大切な人を守る」
taisetsu na hito o mamoru / to protect someone important

But 「守る」 is also used when you follow something that has been decided or agreed upon.

For example:

• 「ルールを守る」 — to follow the rules
• 「規則を守る」 — to obey regulations
• 「時間を守る」 — to be punctual / keep to the agreed time
• 「秘密を守る」 — to keep a secret
• 「約束を守る」 — to keep a promise

Maria did not go against the agreement to meet at three.

That is why we can say:

「マリアは約束を守った。」
Maria wa yakusoku o mamotta.
“Maria kept her promise.”

What Happens in Other Situations?

「約束を守る」 is not limited to meeting friends.

Let’s change the setting.

At School

A teacher tells a student:

「レポートは金曜日までに出してください。」

“Please submit your report by Friday.”

The student replies:

「はい。必ず出します。」

“Yes. I definitely will.”

On Friday, the student submits the report as promised.

The teacher might say:

「ちゃんと約束を守りましたね。」

“You kept your promise.”

The important point is that the student did what they had previously said they would do.

At Home

A parent says to a child:

「ゲームをする前に宿題をするって約束したよね？」

“You promised to do your homework before playing games, remember?”

If the child finishes the homework first:

「約束を守った。」
“They kept the promise.”

But if the child starts playing games without doing the homework:

「約束を破った。」
“They broke the promise.”

Here, 「守る」 and 「破る」 describe opposite outcomes.

At Work

Suppose you tell a client:

「明日の午前中までに資料を送ります。」

“I’ll send the documents by tomorrow morning.”

If you actually send them by then:

「約束を守った。」
“You kept your promise.”

If you fail to do so:

「約束を守れなかった。」
“I couldn’t keep my promise.”

or:

「約束を破ってしまった。」
“I ended up breaking my promise.”

The situations are different, but the core idea remains the same: you either act according to what was previously agreed, or you do not.

What If We Replace 「約束を守る」 with 「約束をする」?

Let’s return to the café.

Maria said:

「約束は守らないと。」

“You have to keep your promises.”

What if she said:

「約束はしないと。」

This would mean something quite different.

「約束をする」
yakusoku o suru / to make a promise

is used when the promise itself is being created.

For example:

「来週、またここで会う約束をした。」

Raishū, mata koko de au yakusoku o shita.

“We promised to meet here again next week.”

At this point, the speakers are making an agreement about the future.

It helps to imagine the sequence:

「約束をする」
make a promise

↓

do what you said you would do

↓

「約束を守る」
keep the promise

The noun 「約束」 is the same, but the verb tells us which stage of the promise we are talking about.

How Is 「約束を果たす」 Different?

Another important expression is:

「約束を果たす」
yakusoku o hatasu / to fulfill a promise

「守る」 and 「果たす」 are similar because both can describe actually doing what you promised.

But their nuance is slightly different.

Imagine a father tells his son:

「いつか北海道へ連れて行くよ。」

“I’ll take you to Hokkaido someday.”

Several years later, they finally make the trip.

You can say:

「父は約束を守った。」

“His father kept his promise.”

But you can also say:

「父は約束を果たした。」

“His father fulfilled his promise.”

「果たす」 often gives a stronger sense of bringing something to completion or finally accomplishing what was promised.

This makes it especially natural with important promises or promises that have existed for a long time.

For example:

「必ず故郷に戻るという約束を果たした。」

“He fulfilled his promise to return to his hometown.”

「優勝して帰ってくるという約束を果たした。」

“She fulfilled her promise to return as the champion.”

「子どものころに交わした約束を、二十年後に果たした。」

“They fulfilled a promise they had made as children twenty years later.”

For ordinary daily agreements, 「守る」 is often more natural.

「待ち合わせの時間を守る。」

“Be on time for an appointment.”

「毎日連絡するという約束を守る。」

“Keep the promise to contact someone every day.”

「借りたお金を今月返すという約束を守る。」

“Keep the promise to repay borrowed money this month.”

Using 「果たす」 is not necessarily grammatically wrong in every such situation, but it may sound more dramatic than the situation requires.

「約束を破る」 Goes in the Opposite Direction

Now imagine that Maria does not appear at three.

Four o’clock comes, and she finally sends a message:

「ごめん。今日は行けなくなった。」

“Sorry. I can’t make it today.”

Kenta might feel:

「約束を破られた。」

“My promise with her was broken.”
More naturally in English: “She broke her promise to me.”

The expression is:

「約束を破る」
yakusoku o yaburu / to break a promise

Here, 「破る」 represents going against what was agreed.

This makes it useful to remember the pair:

「約束を守る」
to keep a promise

「約束を破る」
to break a promise

A similar contrast appears with rules:

「ルールを守る」
to follow the rules

「ルールを破る」
to break the rules

Learning these expressions as pairs makes them easier to understand and remember.

What About 「約束を交わす」?

Another expression similar to 「約束をする」 is:

「約束を交わす」
yakusoku o kawasu / to exchange promises, to make a mutual promise

For example:

「二人は五年後に再会する約束を交わした。」

Futari wa go-nen-go ni saikai suru yakusoku o kawashita.

“The two made a promise to meet again five years later.”

Its basic meaning is close to 「約束をする」, but 「交わす」 emphasizes an exchange between two or more people.

For example:

「友達と約束をした。」

“I made a promise with my friend.”

This sounds completely natural in everyday conversation.

By contrast:

「友達と約束を交わした。」

“I exchanged a promise with my friend.”

This sounds more literary and gives greater weight to the promise itself.

You may encounter 「約束を交わす」 in novels, news articles, narratives, and formal writing.

Learn the Verbs as a Story

You do not have to memorize all the verbs used with 「約束」 as unrelated vocabulary.

Think of them as stages in a story.

First, people decide something:

「約束をする」
to make a promise

「約束を交わす」
to exchange promises

Then they act.

If they do what they promised:

「約束を守る」
to keep a promise

「約束を果たす」
to fulfill a promise

If they do not:

「約束を破る」
to break a promise

Thinking about what happens before and after the promise helps you choose the natural verb.

Knowing Only the Meaning of 「約束」 Is Not Enough

When studying Japanese, learners sometimes memorize vocabulary like this:

「約束」 = promise

Knowing the meaning is important, but real Japanese rarely consists of isolated nouns.

Nouns combine naturally with certain verbs.

With 「約束」, useful combinations include:

• 「約束をする」 — make a promise
• 「約束を交わす」 — exchange promises
• 「約束を守る」 — keep a promise
• 「約束を果たす」 — fulfill a promise
• 「約束を破る」 — break a promise

The same principle appears throughout Japanese.

For example:

• 「期限を守る」 — meet a deadline
• 「規則を守る」 — follow regulations
• 「秘密を守る」 — keep a secret
• 「責任を果たす」 — fulfill one’s responsibility
• 「義務を果たす」 — fulfill one’s duty

Instead of memorizing only 「守る」 or 「果たす」, learn what kinds of nouns naturally appear with them.

This will help both your reading and your speaking.

How to Think About These Expressions on the JLPT

In JLPT vocabulary questions, looking only at the verb can make the choices confusing.

Consider this sentence:

「田中さんは『来月までに必ず返す』と言った。その約束を最後まで＿＿＿。」

Tanaka-san wa “raigetsu made ni kanarazu kaesu” to itta. Sono yakusoku o saigo made ______.

“Tanaka said, ‘I’ll definitely return it by next month.’ He ______ that promise to the end.”

Suppose the choices include:

• 守った
• 建てた
• 開いた
• 飾った

The natural answer is:

「守った」

But at N3–N2 level, the alternatives may be much closer in meaning.

In that situation, do not look only at the verb.

Look at the noun before it.

Here, the noun is:

「約束」

Then ask:

“What verbs naturally go with 約束?”

Also look at what happened earlier in the sentence.

Tanaka already said:

「来月までに必ず返す。」

“I’ll definitely return it by next month.”

The promise has already been made.

So this is no longer the stage of 「約束をする」.

The question is whether he carried it out.

Following the timeline of the sentence helps you identify the natural expression.

What If Both 「守る」 and 「果たす」 Seem Possible?

This is where imagining the situation becomes especially useful.

If the sentence is mainly about following an everyday agreement or not going against a rule, 「守る」 is often natural.

For example:

「毎晩十時までに帰るという約束を守る。」

“Keep the promise to come home by ten every night.”

But if the sentence emphasizes finally accomplishing something promised long ago, 「果たす」 often fits better.

For example:

「亡くなった祖父との約束を、二十年後ようやく果たした。」

Nakunatta sofu to no yakusoku o, nijūnen-go yōyaku hatashita.

“Twenty years later, he finally fulfilled the promise he had made to his late grandfather.”

A simple dictionary translation may not show you this difference clearly.

The situation does.

Who made the promise?

When was it made?

What happened afterward?

When you imagine that sequence, the natural verb becomes easier to see.

Back to the Café

Let’s return once more to the opening scene.

It is Saturday afternoon.

Maria arrives at the café just before three.

She says:

「だって、三時に会うって約束したでしょう。約束は守らないと。」

“But we promised to meet at three, right? You have to keep your promises.”

Before reading this article, you may have simply memorized 「約束を守る」 as a fixed phrase.

Now, however, you can see the story behind it.

Kenta and Maria had already made the promise.

Maria then acted according to that agreement.

That is why Japanese uses:

「約束を守る」

If they are deciding next week’s plans now:

「約束をする」

If someone finally accomplishes an important promise made many years ago:

「約束を果たす」

If someone fails to do what was agreed:

「約束を破る」

The noun remains 「約束」.

The verb changes because the situation changes.

Understand the Meaning, Then Test It in Context

On the JLPT, simply knowing that 「約束」 means “promise” is not always enough.

Ask yourself:

Is the person making a promise?

Are they doing what they promised?

Are they finally fulfilling a long-standing promise?

Or are they breaking it?

Instead of reading words one by one, imagine the situation created by the whole sentence.

That habit will help you not only with vocabulary questions but also with reading comprehension.

RJT (Rapid Japanese Training) gives you a chance to test expressions like these in actual questions.

Once you understand an expression, the next step is to see whether you can choose the most natural Japanese expression from context.

https://rapid-jt.com/