noritugi ni ha syukuhakuentyou ga hituyou desu.

乗り継ぎ means a transfer or a connection, especially in travel.

It comes from the verb 乗り継ぐ, which means to change from one bus/train/plane to another and continue the trip.

So in this sentence, 乗り継ぎ is being used as a noun:

• 乗り継ぎ = transfer / connecting travel

This is common in transportation contexts such as airports, trains, and buses.

には is a combination of two particles:

• に marks the situation, occasion, or target
• は marks the topic and can add a slight contrast

So 乗り継ぎには means something like:

• for a transfer
• in the case of a transfer
• when it comes to transfers

The は often gives a nuance like as for transfers... or at least in the case of transfers...

So the sentence is not just stating a fact about 宿泊延長. It is specifically saying that for transfers, that is what is necessary.

宿泊延長 is a compound noun:

• 宿泊 = lodging / staying overnight
• 延長 = extension

Together, 宿泊延長 means an extension of lodging/stay or an extended hotel stay.

In natural English, depending on context, it could mean:

• an extra night’s stay
• extending your accommodation
• a lodging extension

This kind of compound noun is very common in Japanese, especially in formal writing, notices, and travel-related language.

Because with 必要です, the thing that is necessary is often marked with が.

So:

• 宿泊延長が必要です = an extension of stay is necessary

This is a very common pattern:

• 予約が必要です = a reservation is necessary
• パスポートが必要です = a passport is necessary
• 申請が必要です = an application is necessary

English often says you need X, but Japanese often structures it more like X is necessary.

That is why が is natural here.

必要 is usually treated as a na-adjective in Japanese grammar, though it also behaves noun-like in some situations.

In this sentence:

• 必要です = is necessary

You can also see it before a noun with な:

• 必要な書類 = necessary documents

So:

• before a noun: 必要な
• at the end of a sentence: 必要です

That means:

• 宿泊延長が必要です = An extension of stay is necessary.

You do not say 必要い, because it is not an i-adjective.

That is normal in Japanese. The person involved is often omitted when it is obvious from context.

So this sentence does not explicitly say:

• who needs the extension
• who must arrange it
• whose stay is being extended

It simply states the requirement itself.

Depending on context, the implied meaning could be:

• you need to extend your stay
• passengers need an overnight extension
• a lodging extension is required for transfers

Japanese often leaves out subjects like you, we, or they when the context makes them clear.

Because 必要です already works as the main predicate of the sentence.

Japanese does not need an extra verb here.
The structure is:

• X が 必要です = X is necessary

So the sentence is complete as it is:

• 宿泊延長が必要です

You could express a similar idea in other ways, such as:

• 宿泊延長がいります = you need a stay extension
• 宿泊延長をする必要があります = it is necessary to extend the stay

But 宿泊延長が必要です is shorter and sounds very natural in formal or informational language.

Yes, often a slight contrastive nuance.

乗り継ぎに宿泊延長が必要です would sound more like a neutral statement tied to the situation.

乗り継ぎには宿泊延長が必要です can sound more like:

• for transfers, an extension of stay is necessary
• at least in the case of transfers, this is required

This can imply a contrast such as:

• for direct travel, maybe it is not necessary
• for some other cases, the rule may be different

Sometimes this contrast is strong, and sometimes it is just a natural topic marker. It depends on context.

A very literal breakdown is:

• 乗り継ぎ = transfer / connection
• に = for / in / at
• は = as for
• 宿泊延長 = extension of stay
• が = subject marker
• 必要 = necessary
• です = polite copula

So the overall structure is roughly:

As for transfers, an extension of stay is necessary.

This is a good example of how Japanese often builds sentences around:

• a topic
• the thing being described
• a final predicate like 必要です

Yes. Here are some close alternatives:

• 乗り継ぎには宿泊延長が必要です。
  Formal, compact, natural for notices or travel information.

• 乗り継ぎには延泊が必要です。
  Similar meaning, using 延泊, which often means extended stay or extra nights.

• 乗り継ぎの場合は、宿泊を延長する必要があります。
  More explicit: In the case of a transfer, it is necessary to extend the stay.

The original sentence sounds concise and a bit formal, which is very common in signs, rules, and service announcements.