The most common greeting or expression for welcoming someone into a new country would be the term: "Welcome to _________!"
In this case, we are welcoming someone who went to work in Japan. So you could say something like this:
"Welcome to Japan! We are very happy to have you here! I hope you enjoy your stay!"
Welcome to Japan!
日本へようこそ！
新しい国などに、誰かを迎える時などに一番よく使われる表現は、次のようになります。
"Welcome to _________!"
（～へようこそ！）
この場合、日本へ働きに来た人を歓迎するので、次のように言うことが出来ます。
【例】
"Welcome to Japan! We are very happy to have you here! I hope you enjoy your stay!"
（日本へようこそ！お迎え出来て光栄です！日本滞在を楽しんでください！）
I would like to welcome you to Japan. I hope you enjoy your visit.
Most people would say welcome to Japan, but there are other more formal ways to welcome someone. For example:
I would like to welcome you to Japan. I hope you enjoy your visit.
This can be used when are welcoming someone important for like a special guest.
大抵の人は「Welcome to Japan」と言うと思いますが、よりフォーマルな言い方もできます。例えば：
I would like to welcome you to Japan. I hope you enjoy your visit.
〔訳〕ようこそ日本へいらっしゃいました。日本での滞在が楽しいものになることを願っています
これは、重要な人（例えば、特別なお客さん）を迎える時に、使えます。
Welcome! I hope that you enjoy your stay here in Japan!
Welcome is the way to invite someone somewhere and say that you want them to be comfortable and happy. In the first sentence, it mentions all of Japan, since it is possible that your co-worker might be traveling to several parts of Japan.
The second example reinforces that you really want them to have a good time and to be happy and comfortable while they are in Japan. It is a little more formal.
Welcome, I hope you feel at home during your stay.
Welcome to Tokyo! - You can say Japan or the city name. It's a very basic phrase, however, if the you know the person has already visited you can say "Welcome back to Japan".
Welcome, I hope you feel at home during your stay. - This is quite common with foreign visitors, people say "I hope you feel at home" which means to be comfortable & enjoy their visit.
"Welcome to Tokyo!"（東京へようこそ！）―東京以外に、日本または都市名を入れてもいいでしょう。とてもシンプルなフレーズですが、もし初めての来日でなければ、"Welcome back to Japan"（日本へまたようこそお出で下さいました）と言ってもいいでしょう。Welcome backは「おかえりなさい」という意味です。
"Welcome, I hope you feel at home during your stay."（ようこそ！くつろいで行って下さいね。）外国人訪問客に対してよく使う挨拶言葉です。"I hope you feel at home"とは、心地良い楽しい滞在になりますように、という意味が込められています。
"Welcome to Japan!"
This simply says hello and welcome.
"Welcome to my country, Japan!"
This says directly from you personally, if Japan is the country you are from.
"Welcome to Japan, enjoy your stay!"
This is more like a message, welcome and enjoy your stay.
例文
"Welcome to Japan!"
（日本へようこそ）
「こんにちは、ようこそ」とシンプルに言っています。
例文
"Welcome to my country, Japan!"
（私の国、日本へようこそ）
もし日本があなたの母国であれば、個人的に直接的に言っています。
例文
"Welcome to Japan, enjoy your stay!"
（日本へようこそ、良い滞在を！！）
どちらかと言うと「ようこそ、良い滞在を！！」というメッセージのような感じです。
1. Welcome to the land of the Rising Sun!
The name, "Land of The Rising Sun" was given to Japan
by the ancient Chinese many years ago when Japan first
came into existence. They called it the Land of the Rising
Sun because when they looked towards the direction of Japan
in the early morning, then they looked at the dawn or the
rising sun. Most foreigners are familiar with this term for
Japan.
2. A very warm welcome to my country!
To give someone a warm welcome, means to greet them
in a very friendly and cordial manner which instantly makes
them feel comfortable.
Welcome to Japan, I hope you enjoy your time here.
Welcome to my country Japan!
When someone is visiting Japan, you could greet them with WELCOME TO JAPAN!
This is a nice friendly way of welcoming them to the country, you could make it extra friendly and say I hope you enjoy your time here to make them feel more at home during their stay.
'Good wishes to you on your arrival in Japan' is a welcoming phrase for someone just arriving in your home country to work there. Or it could be someone moving to Japan to live there.
People enjoy being welcomed. It feels really nice when you arrive in a new place and somebody says welcome to you. It makes you feel happy, respected and acknowledged. It is important to welcome somebody when they are new, in your workplace for example.
These two sentences are a very polite way of welcoming someone in any situation. The first one is more informal than the second one.
アメリカ合衆国 
イギリス 
オーストラリア 
南アフリカ 
ドイツ 
ブルガリア 
日本 
アイルランド 
