Business Japanese emails : Subject Lines are key! Mastering Subject Lines & 【 】 to Get Noticed

When writing business emails, do you give enough thought to the subject line? Or do you just jot something down without thinking much about it?

In fact, the subject line plays a crucial role in ensuring your email actually gets read.

Writing a short, clear subject line that explains exactly what’s inside is a great way to show consideration for the recipient.

In Japanese business culture, this small act of thoughtfulness leads to building long-term trust.

＼Japanese business etiquette／
「日本で働くためのビジネス基礎講座きそこうざ」

Are Subject Lines the Key?

If you’ve just started working in Japan or are planning to, you’re likely working hard to master “Keigo” (honorific Japanese) to write professional emails.

Of course, Keigo is important. However, no matter how perfect your Keigo is, your email might not even be opened if the subject line is unclear.

In Japanese business, the subject line is critical.

So, why is the subject line so important?

A Massive Volume of Emails

It is said that the average office worker in Japan receives between 50 and 100 emails every day.

When they open their computers in the morning, they are faced with a mountain of messages.

With so many to go through, there simply isn’t enough time to read every single one in detail.

That’s why people first scan the “subject lines only” to filter them into two categories: “read now” and “read later.”

For example, if you need an urgent reply, you must be strategic—perhaps by including keywords like “Urgent” (至急しきゅう).

Without this extra effort, your email might get buried in their overflowing inbox.

Keep it Short and Clear

Subject lines should be brief and easy to understand so the recipient knows exactly what the email is about at a glance.

Ideally, your subject line should convey:

Putting extra thought into your subject line does more than just share information—it supports the recipient by helping them work more efficiently.

Put Yourself in the Recipient’s Shoes

Japanese culture is rooted in the spirit of “Omotenashi” (hospitality) and “Omoiyari” (thoughtfulness)—the practice of seeing things from another person’s perspective.

This applies not only to customer service but to business emails as well.

Think of it this way: “I want to save my busy colleague even a single second, so I’ll write a subject line that explains the content without them even having to open the mail.”

These small acts of consideration add up.

They lead to a reputation of being “thorough and professional” and “someone who can be trusted.”

While using correct Keigo is wonderful, showing that you value the other person’s time is equally essential for building trust in a Japanese company.

Make Effective Use of 【 】

You may have noticed Japanese business emails with subject lines containing bracketed words like 【重要じゅうよう】 (Important) or 【ご相談そうだん】 (Consultation).

These specific brackets are called “Sumitsuki Kakko” (ink-filled brackets).

They are a very common symbol used in Japanese business emails to make certain words stand out.

Why Use 【】?

The main reason is to make the subject line stand out.

Japanese is a unique language that mixes three types of characters: Kanji, Hiragana, and Katakana.

When you look at an inbox, it’s filled with a dense wall of text.

If you simply write “Important Notice” in plain text, it easily gets lost among all the other characters.

By using 【 】, that part of the subject line becomes visually distinct and immediately catches the recipient’s eye.

It helps them instantly recognize the purpose of your email as soon as they scan their inbox.

Setting Priorities

These brackets play a crucial role in helping the recipient decide how to prioritize your email amidst a flooded inbox.

By using 【 】, you allow the recipient to determine the priority level before they even open the message.

In Japan, minimizing the burden on others is a key element of “good manners.”

Don’t Overdo It!

While【 】 are incredibly useful, be careful not to overuse them.

Attaching 【 】 to every single email is not recommended.

If you do this, the recipient will stop being able to distinguish what is truly “Important” or “Urgent.”

Use 【 】 strategically—specifically when you need someone to prioritize a task, or when you want to clarify that no reply is necessary.

They are meant to make the purpose of your email crystal clear.

Commonly Used 【 】 Brackets

As mentioned earlier, these brackets clarify the purpose of your email. Here is a summary of the most common ones:

1. When requesting an “Action”

Use these when you need the recipient to do something. This is the most common category.

2. When Urgency or Importance is High

Use these for messages that require immediate attention.

3. When sharing Information only

This is a “kindness” that removes the pressure of having to reply.

4. For Non-Task related content

This puts the recipient at ease by showing the email isn’t a new work request.

5. For Regular Updates

Helps the recipient organize their inbox easily.

Examples of Subject Lines Using 【 】

Now that you understand what each bracket means, let’s look at how to use them in real-life situations.

Here are some common examples used in Japanese business.

1. When Requesting an Action

Used when you clearly need the recipient to do something.

2. When Urgency or Importance is High

Use these only for truly critical matters to avoid causing unnecessary alarm.

3. When Sharing Information

Used for broadcasting to multiple people or when no reply is required.

4. For Non-Task related content

Brackets are also helpful for expressing gratitude or providing seasonal greetings.

Conclusion

In this article, we’ve explored the importance of subject lines in Japanese business emails and how to effectively use 【 】 (Sumitsuki Kakko).

The key is to always write your subject line with the recipient in mind.

These small acts of consideration accumulate over time and are essential for building trust in the workplace.

Many Japanese language learners feel anxious about using “perfect” Keigo.

While correct Japanese is certainly important, even the most polite email might go unread if the subject line is unclear.

To ensure your message gets through, try to focus on being thoughtful and clear with your subject lines.

Your effort to be “kind” to the reader will surely be appreciated!

To help you overcome these challenges, mailun-lab offers specialized learning materials for Japanese business email writing.

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”Business Japanese Email Materials" by Former HR & Teacher | mailun-labStruggling with Japanese business emails? Perfect for JLPT N3+ learners, our materials created by an ex-HR expert cover not just phrases, but the cultural logic behind them. Improve your professional skills with our self-study guides. Subscribe today for a free "Basics" textbook!...