ane ha senmendai de kesyou wo sinagara uta wo utatte ita.

は marks 姉 as the topic of the sentence.

So 姉は means something like as for my older sister... or my older sister... in natural English.

A few useful points:

• は is not exactly the same as an English subject marker.
• It sets up what the sentence is about.
• In many sentences like this, the topic is also the person doing the action, so it can feel very close to the subject.

So here, 姉は tells us that the rest of the sentence is describing what the older sister was doing.

Because で marks the place where an action happens.

In this sentence, the older sister is doing makeup and singing at the sink/vanity area, so で is the correct particle.

• 洗面台で = at the sink / at the washstand / at the vanity
• に is more often used for:
  • destination: 学校に行く = go to school
  • existence: 机の上に本がある = there is a book on the desk

Since this is the location of an action, で is the natural choice.

洗面台 usually means a washstand, sink area, or bathroom vanity.

It is not exactly the whole bathroom. It specifically refers to the area with the sink and mirror where someone might:

• wash their face
• brush their teeth
• do their hair
• put on makeup

That is why it fits very naturally with 化粧をする.

化粧 is a noun meaning makeup or cosmetic preparation, and する turns it into the action to put on makeup / to do one’s makeup.

So:

• 化粧 = makeup
• 化粧をする = to put on makeup

The particle を marks 化粧 as the thing involved in the action.

This pattern is very common in Japanese:

• 勉強をする = to study
• 掃除をする = to clean
• 練習をする = to practice

So 化粧をする is just a standard noun + をする structure.

ながら means while doing and connects two actions done by the same person at the same time.

Here:

• 化粧をしながら = while doing her makeup

It is attached to the stem of the verb:

• する → しながら
• 食べる → 食べながら
• 読む → 読みながら

So the pattern is:

• verb stem + ながら

In this sentence, the older sister is doing one action while also doing another.

In AながらB, the B part is usually the main action, and A is the accompanying or background action.

So here:

• 化粧をしながら = while doing her makeup
• 歌を歌っていた = was singing

That means the sentence is centered a little more on the idea that she was singing, with doing her makeup as the simultaneous action.

English often works similarly:

• She was singing while doing her makeup.

The key part is 歌っていた, which is the past form of ～ている.

• 歌う = to sing
• 歌っている = is singing / sings (in progress, depending on context)
• 歌っていた = was singing

Here, ～ていた shows an action that was ongoing in the past.

So this is not just she sang, but rather she was singing.

That fits well with ながら, because both actions are happening at the same time in the past.

Yes, it is a little repetitive if translated literally as sing a song, but it is a normal and common Japanese expression.

• 歌 = song
• 歌う = to sing
• 歌を歌う = to sing a song / to sing

Japanese often uses this kind of noun + matching verb combination.

In context, 歌っていた by itself could also work, but 歌を歌っていた is perfectly natural and can sound a bit more explicit or complete.

Similar patterns exist in English too:

• dream a dream
• smile a smile (poetic)
• sing a song

So even though it looks repetitive, it is not strange Japanese.

Yes, it could.

• 姉は洗面台で化粧をしながら歌っていた。 = also natural

The version with 歌を is simply more explicit. It highlights the act of singing a song a little more clearly.

So:

• 歌っていた = was singing
• 歌を歌っていた = was singing a song / was singing

Both are fine; the original just uses the fuller expression.

In a sentence like this, 姉 usually means my older sister or the speaker’s older sister, unless context shows otherwise.

A useful cultural/grammar note:

• 姉（あね） is commonly used when talking about your own older sister to someone else.
• お姉さん is often used for someone else’s older sister, or as a polite/general term.

So here, the most natural interpretation is my older sister.

Because Japanese very often leaves out words that are clear from context.

Once 姉 is introduced as the topic, Japanese does not need a pronoun like she.

English usually needs a subject in every clause, but Japanese often does not. That is why the sentence can simply describe what 姉 was doing without repeating a pronoun.

This is one of the most common differences between English and Japanese.

Yes. With ながら, the normal rule is that both actions are done by the same subject.

So in this sentence, the one:

• doing makeup
• singing

is the same person: 姉.

You would not normally use ながら if one person was doing makeup and another person was singing.

The readings are:

• 姉 = あね
• は = wa as a particle
• 洗面台 = せんめんだい
• で = de
• 化粧 = けしょう
• を = o
• しながら = shinagara
• 歌 = うた
• を = o
• 歌っていた = utatte ita

So the whole sentence is read:

あね は せんめんだい で けしょう を しながら うた を うたって いた。

Yes.

• 歌った = sang
• 歌っていた = was singing

Using ～ていた gives a sense of an action that was in progress at that time. It helps create a scene, almost like the speaker is describing what they saw.

That works especially well with while doing makeup.

So the sentence feels like:

• she was in the middle of doing her makeup
• and at the same time, she was singing

rather than simply reporting a finished action.