Custom labels are not translated

Question

I created a lightning web component(LWC) with custom labels.
And I also set translation with these labels. (My default lang is Japanese, and translation is English).

But I found these labels is always showing itself in English, even though lang and locale is set to ja and ja_JP correctly.

This behavior is same on LightningApp and Visualforce with lightningOut.

How can I get the correctly tranlated labels?

Here is sample code and meta.

force-app/main/default/lwc/labelTest/labelTest.js

import { LightningElement, track } from 'lwc';
import translate from '@salesforce/label/c.translate';
import lang from '@salesforce/i18n/lang';
import locale from '@salesforce/i18n/locale';

export default class LabelTest extends LightningElement {
  @track translate = translate;
  @track info = {
    lang,
    locale,
  }
}

force-app/main/default/labels/CustomLabels.labels-meta.xml

<?xml version="1.0" encoding="UTF-8"?>
<CustomLabels xmlns="http://soap.sforce.com/2006/04/metadata">
    <labels>
        <fullName>translate</fullName>
        <language>ja</language>
        <protected>true</protected>
        <shortDescription>翻訳</shortDescription>
        <value>翻訳する</value>
    </labels>
</CustomLabels>

force-app/main/default/translations/en_US.translation-meta.xml

<?xml version="1.0" encoding="UTF-8"?>
<Translations xmlns="http://soap.sforce.com/2006/04/metadata">
    <customLabels>
        <label>Translate</label>
        <name>translate</name>
    </customLabels>
...
</Translations>

force-app/main/default/translations/ja.translation-meta.xml

<?xml version="1.0" encoding="UTF-8"?>
<Translations xmlns="http://soap.sforce.com/2006/04/metadata">
    <customLabels>
        <label><!-- 翻訳する --></label>
        <name>translate</name>
    </customLabels>
...
</Translations>

This gives me below.

Please help me!

Answer 1

I did try and error after this post.
I solved this somewhat.

While in my question, jp translation is commented out as default.
However I changed it to the same as the custom label value (looks like below), I got correct label.

<?xml version="1.0" encoding="UTF-8"?>
<Translations xmlns="http://soap.sforce.com/2006/04/metadata">
    <customLabels>
        <label>翻訳する</label>
        <name>translate</name>
    </customLabels>
...
</Translations>

But I think this behavior is different from other salesforce services.