kono keikaku ni douisimasu.

It is read:

この けいかく に どういします。

In a more natural Japanese written form, you would usually see it without spaces:

この計画に同意します。

Romanization:

Kono keikaku ni dōi shimasu.

That’s right—Japanese normally does not use spaces between words.

So the standard written sentence is:

この計画に同意します。

Spaces are often added in textbooks or beginner materials to make the structure easier to see.

この means this, but it must come before a noun.

So:

• この計画 = this plan

A very important beginner point:

• この
  • noun → this + noun
• これ = this by itself

So you can say:

• この計画 = this plan

but not:

• この alone, if you mean this one

For this one, you would use これ.

Because この is modifying 計画.

• 計画 = plan
• この計画 = this plan

Without この, the sentence would mean:

• 計画に同意します。 = I agree to the plan / a plan

That can still be grammatical, but この makes it specifically this plan.

Because 同意する normally takes に.

So the pattern is:

• X に 同意する = to agree to X / to consent to X

In this sentence:

• この計画に = to this plan
• 同意します = agree / consent (polite)

So に marks the thing that someone agrees to.

Because 同意する does not usually take を for the thing agreed to.

English learners often expect を because English says agree to something, and they may think of something as a direct object. But in Japanese, verbs choose different particles depending on the expression.

With 同意する, the natural pattern is:

• 案に同意する = agree to a proposal
• 条件に同意する = agree to the terms
• 計画に同意する = agree to the plan

So:

• この計画に同意します。 = correct
• この計画を同意します。 = unnatural / generally incorrect

同意します is the polite non-past form of 同意する.

Breakdown:

• 同意 = agreement, consent
• する = to do

Together, 同意する is a suru-verb, meaning to agree or to consent.

Polite form:

• 同意します

Plain form:

• 同意する

Past forms:

• 同意しました = agreed
• 同意した = agreed (plain)

Negative forms:

• 同意しません = do not agree
• 同意しない = do not agree (plain)

They are similar, but not always identical.

• 同意する often means to agree, to consent, or to give one’s approval/acceptance
• 賛成する often means to be in favor of something

For example:

• その意見に賛成します。 = I agree with / am in favor of that opinion.
• 条件に同意します。 = I agree to the terms / I consent to the conditions.

With 計画, both can sometimes work depending on context:

• この計画に同意します。
• この計画に賛成します。

But the nuance can differ a little:

• 同意します can sound more like formal agreement/consent
• 賛成します can sound more like supporting the idea

Because Japanese often omits the subject when it is clear from context.

So:

この計画に同意します。

can naturally mean:

• I agree to this plan.
• We agree to this plan.
• sometimes even He/She agrees to this plan.

The exact subject depends on context.

In English, you usually need to say the subject. In Japanese, leaving it out is very common and natural.

Yes.

You can say:

私はこの計画に同意します。

That explicitly means:

I agree to this plan.

But in many situations, Japanese prefers the shorter version without 私は, especially when it is already obvious who is speaking.

Because 計画 is not the topic here—it is the thing being agreed to, so it takes に.

Basic structure:

• この計画に同意します。

If you used は, the meaning would change and become more contrastive:

• この計画には同意します。

This sounds more like:

• As for this plan, I do agree with it
• or I agree with this plan, at least

That には often adds contrast or emphasis.

So the original sentence is the neutral, straightforward form.

You can often translate it as to here, as in:

• agree to this plan

But it’s better to think of に as a particle chosen by the verb, not as a word that always has one fixed English meaning.

In different sentences, に can mark many things, such as:

• destination
• time
• target
• indirect object
• point of attachment
• the thing one agrees to, gets used to, objects to, etc.

So in this sentence, に is there because 同意する uses に.

Yes. It is in the polite style because it ends in します.

• 同意します = polite
• 同意する = plain / dictionary form

So:

• この計画に同意します。 = polite
• この計画に同意する。 = plain

The polite form is appropriate in formal speech, business situations, or when speaking respectfully.

Japanese non-past forms cover both present and future, depending on context.

So 同意します can mean:

• I agree
• I will agree
• I consent

In this sentence, the most natural English translation is usually I agree to this plan, but context could also make it more future-oriented.

Yes, 同意します sounds fairly formal, especially compared with more casual ways of expressing agreement.

For example:

• この計画に同意します。 = somewhat formal, direct, clear
• この計画に賛成です。 = I’m in favor of this plan
• いいと思います。 = I think it’s good

So 同意します is a good choice in meetings, documents, contracts, or official discussions.

Yes, both can be used in English depending on context.

But 同意する often leans a little more toward:

• agree to
• consent to

especially in formal situations.

So if this is a business, legal, or official context, I agree to this plan may fit especially well.

Yes, you can, if you want to use the loanword プラン.

But there is a nuance difference:

• 計画 often sounds more like a concrete plan, scheme, or project plan
• プラン can sound more casual or modern, depending on context

So:

• この計画に同意します。 = very standard and formal
• このプランに同意します。 = possible, but the tone may be a little different

The structure is:

この計画 + に + 同意します

Which breaks down as:

• この計画 = this plan
• に = marks what is being agreed to
• 同意します = agree / consent

So the pattern is:

[thing agreed to] + に + 同意する

Examples:

• その提案に同意します。 = I agree to that proposal.
• 条件に同意します。 = I agree to the conditions.
• 契約内容に同意します。 = I agree to the contract terms.

Yes, but it sounds a bit formal and deliberate.

In everyday conversation, people might also say things like:

• この計画、いいと思います。 = I think this plan is good.
• この計画に賛成です。 = I’m in favor of this plan.
• それでいいです。 = That’s fine.

So この計画に同意します。 is natural, but it feels more formal, official, or explicit than very casual conversation.