kainusi ga kyariikeesu wo tukau.

It is read かいぬし.

• 飼い comes from 飼う（かう）, meaning to keep / to raise / to own (an animal).
• 主（ぬし） means owner or master.

So 飼い主 means the owner of a pet or the person who keeps the animal.

One important thing for learners: the reading ぬし for 主 is not the most obvious one if you only know readings like しゅ or おも, so this is a good word to memorize as a whole.

が marks the grammatical subject of the sentence.

So in:

• 飼い主 が キャリーケース を 使う。

the 飼い主 is the one doing the action of using.

A natural grammar breakdown is:

• 飼い主 = pet owner
• が = subject marker
• キャリーケース = carrier case / carry case
• を = object marker
• 使う = use

So the structure is basically:

The pet owner uses the carrier case.

を marks the direct object, meaning the thing that the action is done to.

Here, the verb is 使う (to use), so the thing being used is キャリーケース.

• キャリーケース を 使う
• use a carrier case

This is very common in Japanese:

• 本を読む = read a book
• 水を飲む = drink water
• スマホを使う = use a smartphone

So を is the normal particle to use with a verb like 使う.

Japanese normally puts the verb at the end of the sentence.

English often uses Subject + Verb + Object:

• The owner uses the carrier case.

Japanese often uses Subject + Object + Verb:

• 飼い主 が キャリーケース を 使う。

This is one of the biggest word-order differences between English and Japanese.

So this sentence is very normal Japanese word order.

使う is the plain non-past form.

That means it can express:

• a present/habitual action: uses
• a future action: will use

Which one it means depends on context.

So this sentence could mean:

• The owner uses a carrier case.
• The owner will use a carrier case.

It can also sound like a general statement, such as describing what the owner does in a certain situation.

Japanese non-past forms do not map perfectly onto English present tense.

Yes, は could be used, but the nuance changes.

• 飼い主がキャリーケースを使う。
• 飼い主はキャリーケースを使う。

Very roughly:

• が highlights or identifies the subject: it is the owner who uses it
• は marks the topic: as for the owner, they use a carrier case

In many beginner examples, both can look similar in translation, but they are not exactly the same in nuance.

Use が when you are focusing on who does the action. Use は when 飼い主 is the topic you are talking about.

キャリーケース is a katakana loanword, usually from English carry case or related usage.

Depending on context, it can mean:

• a rolling suitcase
• a carrying case
• a pet carrier

Because the sentence uses 飼い主 (pet owner), many learners will naturally understand キャリーケース here as a pet carrier or carrier case for the animal.

Katakana words often depend heavily on context, so this is a good example of why vocabulary in Japanese is not always a one-to-one match with English.

Yes, it is grammatically complete, but it feels somewhat context-light.

Japanese often allows short, simple sentences like this for practice or description. In real conversation, speakers might add more information, such as:

• 飼い主が猫を入れるためにキャリーケースを使う。

  • The owner uses a carrier case to put the cat in.

• 病院へ行くとき、飼い主がキャリーケースを使う。

  • When going to the hospital, the owner uses a carrier case.

So the original sentence is fine, but in real life it may sound like a basic statement taken from a textbook, exercise, or caption.

No, standard Japanese normally does not use spaces between words.

The sentence would usually be written like this:

飼い主がキャリーケースを使う。

Spaces are often added in learning materials to help beginners see the parts of the sentence more easily.

So the spaced version is for readability and study, not standard writing.

Yes.

• 飼い主がキャリーケースを使う。 = plain style
• 飼い主がキャリーケースを使います。 = polite style

The plain form is used in:

• casual conversation
• dictionary entries
• narration
• textbook examples
• written explanations

The ます form is used in:

• polite conversation
• speaking to strangers
• customer service
• many classroom situations

So if you were saying this politely in conversation, 使います would often be more natural.

飼い主 is specifically used for the person who keeps or owns an animal.

So it is not a general word for any kind of owner.

For example:

• a pet owner = 飼い主
• a shop owner = 店主 or オーナー
• a car owner = 車の所有者
• an owner in a broad sense = 所有者

Because 飼う is used for raising/keeping animals, 飼い主 strongly suggests an animal owner.

Yes, there are two useful things to notice.

1. 飼い is written with okurigana

   • 飼う is the dictionary form
   • in the compound 飼い主, the い remains

2. 主 is read ぬし here
   This may feel irregular if you only know:

   • 主（しゅ）
   • 主（おも）
   • 主人（しゅじん）

So it is best to learn 飼い主（かいぬし） as one vocabulary item rather than trying to guess the reading from the kanji every time.