sasimi to pura wo tabeta ato, sohu ha atatakai otya wo nomimasita.

Because 刺身 と 天ぷら is being treated as one combined direct object: sashimi and tempura.
The particle と connects the two nouns, and then を marks the whole phrase as the thing that was eaten.

So:

• 刺身 と 天ぷら = sashimi and tempura
• 刺身 と 天ぷら を 食べた = ate sashimi and tempura

You do not need to say 刺身を天ぷらを here.

Here, と means and when connecting nouns.

So:

• 刺身 と 天ぷら = sashimi and tempura

This use of と is specifically for linking nouns in a complete list. It sounds like both items are definitely included.

Because あと means after, and when it follows a verb, Japanese normally uses the verb in its plain past form.

So:

• 食べた あと = after eating
• 行った あと = after going
• 見た あと = after seeing

This is a set pattern:

• verb (plain past) + あとで / あと

So 食べた あと is the natural grammar here.

あと means after. It creates a time expression.

In this sentence:

• 刺身 と 天ぷら を 食べた あと = after eating sashimi and tempura

It tells us when the main action happened. The main action is:

• 祖父 は 温かい お茶 を 飲みました = Grandfather drank warm tea

So the sentence structure is basically:

• After eating sashimi and tempura, grandfather drank warm tea.

This is very common in Japanese.

The final verb of the sentence, 飲みました, sets the politeness level of the sentence.
But verbs inside modifying phrases or time clauses often stay in plain form, even in polite speech.

So:

• 食べた あと = plain form inside the after phrase
• 飲みました = polite main verb at the end

This is completely natural Japanese.

A good way to think about it is:

• subordinate part: often plain
• main sentence ending: shows politeness

は marks the topic, while が more strongly marks the subject.

Here, 祖父 は sounds like:

• As for grandfather, ...
• or simply Grandfather ... as the topic of the sentence

This is very natural when introducing what someone did.

If you used 祖父 が, it could sound more focused or contrastive, depending on context, like identifying who drank the tea.

So in a neutral sentence like this, は is very natural.

By itself, 祖父 usually refers to my grandfather or one’s own grandfather in a somewhat formal or dictionary-like way.

Its reading here is そふ.

A very common learner question is how this differs from おじいさん:

• 祖父（そふ） = my grandfather / one’s own grandfather
• おじいさん = grandfather, usually when referring to someone else’s grandfather, or used more generally / directly

So 祖父 は here most naturally means my grandfather as the topic.

The お is an honorific/polite prefix. It often appears on certain everyday words to make them sound more natural or polite.

So:

• 茶 = tea
• お茶 = tea

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

This お does not change the basic meaning very much here; it just makes the word sound natural and standard.

Both 温かい and 暖かい can mean warm, but they are used differently.

• 温かい is used for things like drinks, food, water, body temperature
• 暖かい is used more for weather, air, rooms, climate

So:

• 温かい お茶 = warm tea
• 暖かい 日 = a warm day

For tea, 温かい is the correct choice.

Yes, the most natural interpretation is yes.

In Japanese, when a clause like 刺身 と 天ぷら を 食べた あと appears before the main clause, the subject is often understood from the main clause if no new subject is given.

So the sentence naturally means:

• After grandfather ate sashimi and tempura, he drank warm tea.

If someone else had done the eating, Japanese would usually make that clearer.

Because Japanese often omits subjects and pronouns when they are clear from context.

Once 祖父 は is given, Japanese does not need to repeat he.
The language prefers leaving out information that is already understood.

So instead of something like:

• Grandfather ate ... and then he drank ...

Japanese simply says:

• 祖父 は ... 飲みました

The subject carries over naturally.

Japanese usually puts important grammatical information before the final verb.

This sentence is structured like:

• [After eating sashimi and tempura], [grandfather] [warm tea] [drank].

Broken down:

• 刺身 と 天ぷら を 食べた あと、 = after eating sashimi and tempura
• 祖父 は = grandfather (topic)
• 温かい お茶 を = warm tea (object)
• 飲みました = drank

So the verb comes at the end, which is normal in Japanese.

No. In normal Japanese writing, you would usually write it without spaces:

刺身と天ぷらを食べたあと、祖父は温かいお茶を飲みました。

Spaces are often added in beginner materials to make the sentence easier to read. They help learners see:

• words
• particles
• phrase boundaries

So the spaced version is a teaching aid, not standard adult writing.

Yes. 食べたあと and 食べたあとで are both possible.

• 食べたあと = after eating
• 食べたあとで = after eating

The で can make the timing relationship feel a little more explicit, but in many cases the meaning is basically the same.

So this sentence could also be:

刺身と天ぷらを食べたあとで、祖父は温かいお茶を飲みました。

Both are natural.