raikyaku ga aru node, otya wo youisite okimasu.

来客 is read らいきゃく.

It means a visitor or visitors/guests coming over. In this sentence, it does not strongly focus on one specific person; it can simply mean we’re having company or there will be guests.

So 来客がある is a set-like expression meaning something like:

• There will be visitors
• We have guests coming
• We’re expecting company

が marks 来客 as the thing that exists or occurs.

With ある, が is very common because the sentence is saying that the event/state of having visitors exists:

• 来客がある = There are visitors / We have visitors coming

If you used は, it would sound more contrastive or topic-marking, as if you were setting visitors up as the topic in contrast with something else. In a normal sentence like this, が is the natural choice.

Good question. Yes, actual people normally take いる:

• 人がいる = There is a person / Someone is here

But 来客がある is a conventional expression. Here, 来客 is treated less like an individual person standing there and more like the event/circumstance of receiving visitors.

So:

• 客がいる sounds like there are guests here
• 来客がある sounds more like there will be visitors / we have company

It is more formal and event-like.

Both can mean because, but ので usually sounds a bit:

• softer
• more explanatory
• more neutral/polite

So:

• 来客があるので、お茶を用意しておきます。 = Since we’re having visitors, I’ll prepare tea in advance.

If you used から:

• 来客があるから、お茶を用意しておきます。

that is also correct, but it can sound a little more direct or assertive.

In polite or written-style explanations, ので is very common.

〜ておく is a very important pattern. It means doing something in advance or leaving something done/prepared for a future purpose.

So:

• 用意します = prepare
• 用意しておきます = prepare beforehand / get it ready in advance

In this sentence, the speaker is not just saying I’ll prepare tea. They are saying:

• I’ll get the tea ready ahead of time because visitors are coming.

That in advance nuance comes from 〜ておく.

を marks the direct object of 用意する.

Here, the thing being prepared is お茶:

• お茶を用意する = to prepare tea

So お茶 is what receives the action of preparing.

The お is an honorific/polite prefix. It often appears with common nouns, especially in daily-life words, to make them sound more polite or refined.

• 茶 = tea
• お茶 = tea (more normal/polite in everyday speech)

In modern Japanese, お茶 is much more common than plain 茶 in ordinary conversation.

So while 茶 exists, お茶 is the natural form here.

Japanese often omits the subject when it is understood from context.

So 用意しておきます could mean:

• I will prepare it
• We will prepare it

depending on the situation.

In English, you usually need a subject, but in Japanese it is often left out if it is obvious. Here, the important point is the action, not explicitly who is doing it.

Usually, it suggests that visitors are expected or that the situation of having visitors is the reason for preparing tea.

So the feeling is often:

• We’re going to have visitors
• We have visitors coming

It does not strongly suggest they are already sitting there at this exact moment.

That said, context matters. In some situations it could simply mean we have guests, but because of 用意しておきます, the sentence strongly leans toward preparing in advance.

Yes, 用意しておきます is polite because of ます.

A casual version would be:

• 来客があるので、お茶を用意しておく。

In everyday speech, 〜ておく is also very often contracted:

• 用意しときます = polite spoken contraction of 用意しておきます
• 用意しとく = casual spoken contraction of 用意しておく

So you may hear:

• 来客があるので、お茶を用意しときます。

Japanese often puts the reason before the main action:

• 来客があるので = because there will be visitors
• お茶を用意しておきます = I’ll prepare tea in advance

That order is very natural.

You could rearrange parts in some contexts, but this reason-first structure is standard and easy to understand. Japanese often builds up background information first, then gives the main action or conclusion.

It is understandable and fairly common, but it sounds a bit more formal or set-expression-like than some everyday alternatives.

Depending on context, people might also say things like:

• お客さんが来るので = because guests are coming
• 来客の予定があるので = because we’re expecting visitors

So 来客がある is perfectly correct, but it has a slightly more formal or businesslike feel than お客さんが来る.

Not exactly. 用意する means prepare, not specifically brew or make tea.

So お茶を用意しておきます could mean:

• setting out tea
• preparing tea things
• getting tea ready
• perhaps making tea in advance, depending on context

If you specifically wanted to say make/brew tea, Japanese might use a different verb depending on the nuance.

So prepare tea or get the tea ready is closer to the original.