kinoko ga haitta tenpura ha karukute, sohu mo okawarisite imasita.

In Japanese, a verb in plain form can directly modify a noun. Here, 入った 天ぷら means tempura that had mushrooms in it or tempura with mushrooms inside.

The past form 入った does not necessarily mean the whole sentence is “in the past” in the English sense. In a noun-modifying clause, it often describes a completed state:

• きのこが入った天ぷら = tempura that contains mushrooms / tempura with mushrooms in it

It is similar to how English might say the tempura that had mushrooms in it, even if the main point is simply describing what kind of tempura it was.

Because 入る is an intransitive verb.

• 入る = to enter, to be contained, to go in
• 入れる = to put something in

So:

• きのこが入った = mushrooms went in / mushrooms were inside
• きのこを入れた = someone put mushrooms in

In this sentence, the focus is on the tempura having mushrooms in it, not on who added them, so が is natural.

Yes, in natural English it could often be translated simply as mushroom tempura or tempura with mushrooms in it.

But the Japanese expression is a little more descriptive:

• きのこ = mushrooms
• が入った = that had mushrooms in it
• 天ぷら = tempura

So literally it is something like:

• the tempura that had mushrooms in it

This pattern is very common in Japanese:

• チーズが入ったパン = bread with cheese in it
• あんこが入ったもち = mochi with red bean paste inside

は marks 天ぷら as the topic of the sentence.

So the sentence is talking about as for the tempura with mushrooms in it...

That topic is then followed by comments about it:

• 軽くて = it was light
• 祖父もおかわりしていました = Grandpa also had another helping

So は is not marking the direct subject in the same way English does. It sets up the thing being discussed.

Not usually. With food, 軽い often means:

• light
• not heavy
• not greasy
• easy to eat

So 軽くて here probably means the tempura felt light rather than oily or overly filling.

The -て form connects this idea to the next clause:

• 軽くて、祖父もおかわりしていました。
• It was light, and Grandpa also had another helping.

Depending on context, it can feel like either simple connection (and) or a reason-like connection (because it was light...).

Because 軽い is an i-adjective, and its -て form is 軽くて.

This form is used to connect clauses:

• 軽い = light
• 軽くて = being light / and it was light

This is like saying:

• It was light, and ...
• Because it was light, ...

Other examples:

• 安くておいしい = cheap and delicious
• 大きくてきれい = big and beautiful

も means also or too.

So 祖父も means:

• Grandpa too
• Grandpa also

This suggests that someone else may also have had another helping, or that Grandpa joined in as well.

祖父 is the more neutral word used for my grandfather / one’s grandfather when talking about him to other people.

• 祖父（そふ） = my grandfather / our grandfather
• おじいさん = grandfather / old man, often used when referring to someone else’s grandfather or when addressing a grandfather more directly

So if the speaker is talking about their own grandfather, 祖父 is the natural choice.

おかわり means another helping, a second serving, or seconds.

It often combines with する:

• おかわりする = to have another helping / to get seconds

So:

• 祖父もおかわりしていました = Grandpa was also having another helping / Grandpa also had seconds

In natural English, Grandpa also went back for seconds would fit well.

Because おかわりする works as a fixed expression: a noun plus する.

This is very common in Japanese:

• 勉強する = to study
• 運動する = to exercise
• 電話する = to call
• おかわりする = to have another helping

So おかわりしていました is just the -ていました form of おかわりする.

していました is the past polite form of している, which can show an ongoing action or a situation in progress.

So:

• おかわりした = had another helping
• おかわりしていました = was having another helping / was going back for seconds

In many contexts, -ていました gives a softer, more descriptive feel, as if the speaker is recalling what was happening at that time.

Also, いました makes the sentence polite.

A little, yes—but that is normal.

Parts like:

• 入った
• 軽くて

are plain forms because they are inside a modifier or a clause-linking form.

The sentence ends with:

• していました

which is polite.

This is very common in Japanese. The politeness of the sentence is usually determined mainly by the final verb.

Sometimes yes, but the nuance is different.

• きのこの天ぷら usually means mushroom tempura
• きのこが入った天ぷら means tempura that had mushrooms in it

The second one sounds more specific and descriptive, as if mushrooms were part of the filling or contents of the tempura dish. It emphasizes that mushrooms were included inside it.

So both can be translated similarly in some contexts, but they are not always exactly the same in nuance.