Learn Hardcore Japanese: yane wo naositaato, tenzyou no simi ga kiemasita. - After fixing the roof, the stains on the ceiling disappeared.

屋根 (やね) means “roof.”
を marks 屋根 as the direct object of the verb 直す (なおす), “to repair/fix.”
直した is the past tense of 直す, so it means “repaired.”
あと means “after.” When you attach あと to the past-tense verb, you get a time expression: “after having done [that action].”
So 屋根を直したあと = “after having repaired the roof.”

Why is the verb 直す in the past tense before あと?

When you want to say “after doing X,” you put the verb in its past-tense plain form ( ～た form) + あと. That shows X is completed before the next action. If you used the non-past form ( 直すあと), it wouldn’t be grammatically correct for “after.”

Could you use してから instead of したあと? If so, is there any nuance difference?

Yes. You could say 屋根を直してから、天井のしみが消えました。 Both mean “after repairing the roof, the stain on the ceiling disappeared.”

～てから often feels more immediate or sequential: “as soon as I repaired the roof, then…”
～たあと is a bit more neutral/time-stamp-like: “after I’d repaired the roof.”
In most contexts they’re interchangeable.

Why is 天井のしみ using の instead of を?

の here is the genitive or attributive particle linking 天井 (“ceiling”) and しみ (“stain/spots”). It means “the ceiling’s stain” or “stain on the ceiling.” It’s not marking the direct object of the verb; it’s just combining two nouns into one phrase.

Why is が used before 消えました?

が marks 天井のしみ as the grammatical subject of the intransitive verb 消える (“to disappear”). Intransitive verbs describing a change of state normally take が for their subject.

What’s the difference between 消える and 消す?

消える is intransitive: “to disappear,” “to go out,” “to vanish” (subject disappears by itself or by some cause).
消す is transitive: “to erase,” “to turn off,” “to make something disappear.”
Here the stain disappeared on its own once the roof was fixed, so 消える is correct.

Why is there no explicit subject like “I” or “we” in the sentence?

Japanese often omits the grammatical subject when it’s clear from context. Here it’s understood that the speaker (or someone) repaired the roof, so “I/we” is implied in 屋根を直した.

What nuance does this sentence carry about cause and effect?

By sequencing “after repairing the roof” and then “the stain disappeared,” the sentence implies a causal link: fixing the roof solved the leak, so the water stain on the ceiling went away. The listener infers that repairing the roof stopped water intrusion, hence the stain vanished.

Why is there a comma (、) between 屋根を直したあと and 天井のしみが消えました?

The comma marks the boundary between the time clause (屋根を直したあと) and the main clause (天井のしみが消えました), making the sentence easier to parse. It’s common to separate clauses with a comma in Japanese.

Can you break down the full sentence literally?

屋根　を　直した　あと、　天井　の　しみ　が　消えました
Roof – (object) – repaired – after, – ceiling – ‘s – stain – (subject) – disappeared.

How would you say this if you wanted to emphasize who repaired the roof?

You could add the agent with が or は, or use a passive:

私が屋根を直したあと、天井のしみが消えました。 (I repaired the roof…)
屋根は私によって直されたあと、天井のしみが消えました。 (After the roof was repaired by me…)

Is it possible to omit 屋根 or 天井のしみ in casual conversation?

Yes. If context is clear, you might say simply:

直したあと、しみが消えた。
Listeners infer you mean the roof repair and the ceiling stain from prior context.