High language proficiency in Japanese is required.
Fluency in Japanese reading, writing, and oral communication is needed.
Both responses can be used to express that proficiency in Japanese is needed. The first fails to mention what specifically, while the second expresses it more in detail. However, the first response also carries more weight, in that someone needs more experience. One can look it in the perspective of, the first response seems to ask for a person with a college level of Japanese, while the second response is more drawn to anyone that is fluent in all three areas. That being said, the first response does not mean that some one is able to write proficiently in Japanese, though they may be able to speak proficiently.
By stating that the person will have to be fluent in Japanese, they should understand that this includes the four language skills (reading, writing, listening, and speaking). Also, using the auxiliary verb "will" communicates that something is necessary or required but isn't so strong. I hope that this helps. :)
"You will need to be fluent in Japanese"（日本語が堪能である必要がある）
これは「リーディング・ライティング・リスニング・スピーキングの四つのスキルにおいて熟達した人」という意味です。
また、助動詞の "will" はここでは、（必要であることに変わりありませんが）「必要」の意味を弱めています。
参考になれば幸いです。
There are different phrases you could use depending on the level you require from the candidate. Note the below are only subtle differences.
You could ask for Japanese "fluency" or for the applicant to be "fluent", meaning they are able to speak, write, read and overall communicate comfortably in Japanese to a near-native level.
If you ask for strong Japanese communication skills, this would imply something similar to above, although may appeal to some who have upper-intermediate skills also.
If you are looking for a strong ability to communicate, but it is not essential to be like a native speaker, you could ask for high or strong "proficiency".
志願者にどの程度のレベルを求めるかによって、これはいろいろなフレーズが使えます。
下記に述べることはほんのわずかな違いです。
"fluency" または "fluent" を使うと、日本語の読み・書き・会話、そしてコミュニケーション全体がネイティブに近いレベルでできないといけないという意味になります。
"strong Japanese communication skills" を使うと、上記と同じようなニュアンスになりますが、これには中上級の人も関心を抱くかもしれません。
しっかりと意思疎通のできる人を求めているものの必ずしもネイティブレベルでなくても良いなら、高度な "proficiency"（技能）を要求してもいいでしょう。
High language proficiency in Japanese is preferred
The two best ways to imply the importance of this are through the words 'must' and 'required'. 'Proficiency' means skill/ability level so a 'high proficiency is needed'. The following sentences can help:
A high language proficiency in Japanese is a must
A high skill level of of Japanese is required
You can also use the word 'preferred', however this is not as strong as 'required' or 'must' and readers may think that also they don't have a high skill. They may still be considered. So be careful!
High language proficiency in Japanese is preferred
この重要性を表すのにうってつけの言葉が二つあります。'must' と 'required' です。
'proficiency' は「熟練度」「能力」という意味です。ですから、'high proficiency' が求められるわけです。
次のように言えます。
A high language proficiency in Japanese is a must
A high skill level of Japanese is required
（高い日本語能力が必要）
'preferred' という言葉も使えますが、これは 'required' や 'must' ほど強くありません。ですから、あまりスキルの高くない人にもチャンスがあると思われるかもしれません。なので、気をつけてください！
High language proficiency in Japanese is preferred
（日本語能力が高いことが望ましい）
An advanced understanding of the Japanese language is required.
Efficiency in the Japanese language is mandatory.
Fluency in Japanese is a must.
"Fluent in _______" (Japanese) is the most common phrase used to describe this ability.
Fluent - Of a foreign language; spoken accurately and with facility
On a job's requirements you may see phrases like this.
-An advanced understanding of the Japanese language is required.
-Efficiency in the Japanese language is mandatory.
-Fluency in Japanese is a must.
"Fluent in _______" がこの能力について表す最も一般的なフレーズです。
Fluent -〔外国語について〕正確で滑らかに話された
仕事の必須要件の所では、次のようなフレーズを目にするかもしれません。
-An advanced understanding of the Japanese language is required.
-Efficiency in the Japanese language is mandatory.
-Fluency in Japanese is a must.
（日本語が堪能であることは必須条件です）
An advanced level of Japanese fluency is mandatory.
Must be fluent in Japanese
All of these answers are telling the applicant that being fluent or near fluent in Japanese is a requirement.
However, while all of the statements are saying the same thing, the second statement is the strongest. The word "mandatory" takes on connotation of finality. When you see that word, you feel that there is no wiggle room or way to get around it.
The word "required or requirement" has the same meaning, but it may leave the door open a bit. A person that is near the level of proficiency required may feel that there is some way to get by, but with "mandatory" people understand that it is absolutely necessary and non-negotiable.
Excellent communication skills in Japanese are required
Only applicants with native or near native Japanese skills will be considered
When writing requirements for a job in Japan, you want to write that a high level of proficiency in Japanese is required. In that case, you can try one of the above-suggested example sentences which may be appropriate for any given situation. There are always a variety of ways to respond to someone or make a comment - depending on the context and other factors such as nationality, appropriacy and body language
Here are three different ways that we can use to describe a language proficiency for a certain job position. There are many ways you can write this, it all depends on how big you want the sentence to be. "Must be fluent in Japanese," can be useful when just making a footnote, whereas the other two can be used as well if you wanted to be more descriptive.
It is required that you are highly proficient in Japanese.
When going through job requirements for a certain job there are certain things that you will see is a 'must' to have such as;
- Being highly proficient in Japanese.
You could use any of the above two sentences to include in your list of needed requirements.
日本 
カナダ 
アメリカ合衆国 
オーストラリア 
イギリス 
南アフリカ 
