hanami no ato de hakubutukan ni mo yotta node, sono hi ha itinitizyuu yoku arukimasita.

In 花見のあとで, the の links the noun 花見 (flower viewing / cherry-blossom viewing) to あと (after).

So:

• 花見 = flower viewing
• 花見のあと = after the flower viewing

This is a very common pattern:

• 食事のあと = after the meal
• 授業のあと = after class
• 仕事のあと = after work

When a noun comes before あと, you usually connect them with の.

あと means after or later, and で often makes the phrase function more naturally as a time expression in the sentence.

So:

• 花見のあと = after the flower viewing
• 花見のあとで = after the flower viewing / after flower viewing, then...

In many cases, のあと and のあとで are both possible, but あとで often sounds a little more like after that, then...

Here, 花見のあとで博物館にも寄った gives the sense of: After the flower viewing, we also stopped by the museum.

Because 寄る often takes に to mark the place you stop by.

So:

• 博物館に寄る = to stop by the museum
• コンビニに寄る = to stop by the convenience store
• 友達の家に寄る = to stop by a friend’s house

Here, 博物館に marks the destination/place visited briefly.

も means also / too.

So 博物館にも寄った means: (we) also stopped by the museum

The implication is that the speaker did something else in addition to going to the museum — in this sentence, they had already gone to 花見, and then they also stopped by the museum.

Notice how も attaches after the particle:

• 博物館に
  • も = 博物館にも

This is very common in Japanese.

寄った is the past tense of 寄る.

In this sentence, 寄る means:

• to stop by
• to drop in
• to make a brief visit

So 博物館にも寄った means: (we) also stopped by the museum

It does not necessarily mean a long visit. It often suggests going somewhere on the way to or after something else.

Because the action of stopping by the museum happened before the result that follows.

Structure:

• 博物館にも寄ったので
• because (we) also stopped by the museum...

Japanese often uses the plain past before ので when the reason is a completed action.

So the flow is:

1. We went flower viewing.
2. We also stopped by the museum.
3. As a result, we walked a lot all day.

ので means because / so, and it gives an explanatory reason.

Here:

• 博物館にも寄ったので、 = because we also stopped by the museum, ...

Compared with から:

• から can sound more direct or assertive
• ので often sounds a bit softer, more neutral, and more explanatory

So:

• 博物館にも寄ったから、その日は一日中よく歩きました。
• 博物館にも寄ったので、その日は一日中よく歩きました。

Both are grammatical, but ので fits very naturally in this kind of calm explanation.

は marks その日 as the topic: as for that day...

So:

• その日 = that day
• その日は = as for that day / on that day

This helps frame the second part of the sentence:

• その日は一日中よく歩きました
• As for that day, we walked a lot all day

Using は here gives a natural topic-comment structure.

一日中 is read いちにちじゅう and means:

• all day
• throughout the whole day

Examples:

• 一日中寝ていた = I slept all day
• 一日中雨だった = It rained all day

In this sentence, その日は一日中よく歩きました means that the walking continued over the course of the whole day.

This is a very common point of confusion.

よく can mean:

1. well
2. often
3. a lot / considerably

Here, with 歩きました, it means something like a lot or quite a bit.

So:

• よく歩きました = walked a lot

It does not mean walked skillfully here.

Context decides the meaning of よく. Because the sentence is talking about how much they walked during the day, a lot is the natural interpretation.

The subject is omitted, which is very normal in Japanese.

From context, the understood subject is probably:

• I
• we
• or the people being talked about

Japanese often leaves out subjects when they are already understood from the situation.

So instead of saying:

• 私はその日は一日中よく歩きました

the sentence simply says:

• その日は一日中よく歩きました

This is natural and common.

In this sentence, 花見 functions as a noun.

It refers to the activity of flower viewing, especially cherry-blossom viewing.

That is why it can be followed by の:

• 花見のあとで = after flower viewing

Even though it comes from the idea of looking at flowers, it behaves like a noun here.

Yes, but it would create a different structure.

For example:

• 花を見に行ったあとで、博物館にも寄ったので… = After going to see the flowers, we also stopped by the museum, so...

That is more explicitly verbal.

The original sentence uses 花見, which is compact and natural because flower viewing is treated as an event/activity. Japanese often prefers this kind of noun-based expression when talking about events:

• 買い物のあとで = after shopping
• 食事のあとで = after the meal
• 花見のあとで = after flower viewing

The comma is mainly there to make the sentence easier to read.

It separates:

• the reason: 花見のあとで博物館にも寄ったので
• the result: その日は一日中よく歩きました

Japanese punctuation is somewhat flexible, so the sentence could sometimes appear without the comma, especially in casual writing. But with the comma, the structure is clearer.