nokorimono ha reizouko ni irete, asita no hirugohan ni simasu.

It is read のこりもの.

Literally, it means something like remaining things:

• 残り = remainder / what is left
• 物 = thing(s)

In everyday Japanese, 残り物 usually means leftovers, especially leftover food.

は marks 残り物 as the topic of the sentence.

So the sentence is not just talking about any action in general; it is specifically about the leftovers and what will be done with them.

You can think of it like:

• As for the leftovers, we’ll put them in the fridge and have them for tomorrow’s lunch.

A learner may expect を, because the leftovers are also the thing being acted on. But Japanese often uses は when the speaker wants to set something up as the topic first. The object role is understood from the verb.

Here, に marks the destination or place something goes into.

With 入れる (to put in), the place receiving the item is commonly marked by に:

• 冷蔵庫に入れる = put it into the refrigerator

Why not the others?

• へ also marks direction, but with 入れる, に is much more natural.
• で marks the place where an action happens, not the destination. So 冷蔵庫で入れる would not fit here.

入れて is the て-form of 入れる.

Here, the て-form connects actions:

• 冷蔵庫に入れて、明日の昼ご飯にします。
• Put it in the fridge, and make it tomorrow’s lunch.

This is a very common way to link actions in Japanese. It often means:

• and
• then
• sometimes after doing that

So the flow is:

1. Put the leftovers in the fridge
2. Use them for tomorrow’s lunch

Yes. Japanese often leaves out the subject when it is clear from context.

This sentence does not explicitly say:

• I
• we
• someone

Depending on context, it could mean:

• I’ll put the leftovers in the fridge and have them for tomorrow’s lunch
• We’ll put the leftovers in the fridge and have them for tomorrow’s lunch

Japanese frequently omits subjects when they are already understood.

明日の昼ご飯 means tomorrow’s lunch.

Breakdown:

• 明日 = tomorrow
• の = connects nouns, often like ’s or of
• 昼ご飯 = lunch

So:

• 明日の昼ご飯 = tomorrow’s lunch

The の shows that tomorrow is modifying lunch.

Here, 〜にします means to decide on / make something into / use something as.

So:

• 明日の昼ご飯にします means we’ll make it tomorrow’s lunch or more naturally we’ll have it for tomorrow’s lunch.

This does not mean physically creating lunch from scratch. It means deciding that the leftovers will serve as tomorrow’s lunch.

This pattern is common:

• これにします。 = I’ll choose this.
• 夕飯はカレーにします。 = We’ll have curry for dinner.
• 残り物を明日の昼ご飯にする。 = use the leftovers for tomorrow’s lunch

That に marks the result or role something is being assigned.

The idea is:

• make/use the leftovers as tomorrow’s lunch

So the structure is roughly:

• X を Y にする = make X into Y / use X as Y

Even though を is not stated here because 残り物 is the topic with は, the underlying idea is still:

• 残り物を明日の昼ご飯にします

So に is doing the job of marking what it will become / what role it will take.

Both are possible, but they feel different.

• 残り物は focuses on the leftovers as the topic
• 残り物を would focus more directly on them as the object of the action

Compare:

• 残り物は冷蔵庫に入れて、明日の昼ご飯にします。

  • As for the leftovers, we’ll put them in the fridge and use them for tomorrow’s lunch.

• 残り物を冷蔵庫に入れて、明日の昼ご飯にします。

  • Put the leftovers in the fridge and use them for tomorrow’s lunch.

The version with は sounds very natural when introducing what will be done about the leftovers.

Yes, it is in a polite style, because it ends with します.

• dictionary/plain style: する
• polite style: します

However, this sentence is not extremely formal. It is everyday polite Japanese, suitable for normal conversation.

A plain-style version would be:

• 残り物は冷蔵庫に入れて、明日の昼ご飯にする。

Yes, and that is part of why this expression can be tricky.

〜にする often has a broad meaning like:

• decide on
• choose
• make into
• use as

In this sentence, the most natural interpretation is:

• decide to have the leftovers for tomorrow’s lunch
• use the leftovers as tomorrow’s lunch

So it carries both the sense of decision and assignment of role.

The comma mainly shows a pause and makes the sentence easier to read.

It separates the two linked actions:

1. 冷蔵庫に入れて
2. 明日の昼ご飯にします

Japanese punctuation is often somewhat flexible, so the sentence could also appear without the comma:

• 残り物は冷蔵庫に入れて明日の昼ご飯にします。

The meaning does not really change.

Not really. The second part, 明日の昼ご飯にします, strongly suggests the leftovers themselves will become tomorrow’s lunch.

So the natural reading is:

• We’ll store the leftovers in the fridge and eat them for tomorrow’s lunch.

If the speaker meant I’ll put them in the fridge and cook lunch tomorrow, Japanese would normally use a different expression.