直訳に近づけるならば、「日本海」 ＝The sea of Japan
Niigata Prefecture is next to the sea of Japan.
新潟県は日本海に面している。
Niigata Prefecture is on the coast of the sea of Japan.
新潟県は日本海の海岸沿いにある。
日本海にこだわらなければ、west coastの方が外国人にはイメージしやすいかもしれません。
Niigata Prefecture is on the west coast of Japan.
新潟県は日本の西海岸側にある。
To say that something 'faces' something else is to say that it 'points in that direction' or is 'meaningfully oriented in the direction of'. Of course, it comes from the word 'face', which is the place we look when we are sending out our attention to another person.
Niigata is by the Sea of Japan: saying that something is 'by' a location is an alternative way of saying 'close to'. So this means that Niigata is close to the Sea of Japan.
Niigata is on the west coast: We can say that a town or city is 'on' the coast as a way of saying that it is near to the coast.
Niigata is by the Sea of Japan.
（新潟は日本海側にあります。）
'by' とは、 'close to'と同じで、～の近くにという意味です。
Niigata is on the west coast.
（新潟は西海岸にあります。）
'on' the coast は、海岸の近くにという意味です。
Niigata is on the coast of Japan facing the Sea of Japan.
Niigata is a beach-side prefecture next to the Sea of Japan.
Niigata is a coastal prefecture by the Sea of Japan.
There are a few ways to say that a prefecture, city, or place is next to the sea or beach including but not limited to:
Coast (noun) = the part of the land that meets the sea. (E.g. On the coast)
Beach-side (adjective) = being next to a beach (E.g. It is a beach-side prefecture).
Coastal (adjective) = being near the coast. (E.g. Coastal city)
There are also a few ways to say that the sea is the Sea of Japan:
Facing = front being towards each other.
Next to = being beside each other.
By = being beside / next to each other.
都道府県、都市、場所が海やビーチの近くにあることを表す言い方はたくさんあります。
Coast (名詞) = 海に面した場所 (例：On the coast（海岸に）)
Beach-side (形容詞) = ビーチのとなり (例： It is a beach-side prefecture（ビーチ側にある県です。)
Coastal (形容詞) = 海岸の近くにあること (例：Coastal city（沿岸都市）)
日本海側に面していることを表す方法もいくつかあります。
Facing = ～に面している
Next to = ～の隣、横
By = ～の近くに
To describe which side of Japan a city/prefecture is in then you would use the direction (north/south/east/west) You you can simply say 'on the west coast' to be more detailed you could say 'on the sea side of Japan'
ある街／県が日本のどちら側にあるか説明するなら、方角（north/south/east/west）を使います。
シンプルに 'on the west coast'（西海岸に）と言えます。
あるいはより具体的に、'on the sea side of Japan'（日本海側に）と言うこともできます。
When talking about a certain prefecture in Japan (such as Niigata Prefecture), you want to say that the prefecture is on the Sea of Japan side. You may try one of the above suggestions.
___ prefecture is found on the sea close to Japan.
Next to the sea of Japan is the ___ prefecture.
In this case your sentence would be
"Niigata prefecture can be found on the sea side of Japan.
"Next to the sea of Japan is the Niigata prefecture."
以下のように言うことができます。
"Niigata prefecture can be found on the sea side of Japan.
（新潟県は、日本海側にあります。）
"Next to the sea of Japan is the Niigata prefecture."
（日本海側に新潟県があります。）
日本 
アメリカ合衆国 
イギリス 
南アフリカ 
