wasurenai you ni, taisetuna koto ha sugu memosimasu.

ように here means so that or in order not to.

So:

• 忘れない = not forget
• ように = so that

Together, 忘れないように means:

• so that I don’t forget
• in order not to forget

It expresses a purpose or goal.

Before ように, Japanese normally uses the plain form, not the polite ます form.

So:

• 忘れないように = natural
• 忘れませんように = a different expression, often used like I hope... or in set phrases

In this sentence, 忘れないように is just connecting to the main action, so plain form is the standard choice.

In this pattern, ように acts as a fixed grammar expression.

You can think of it as marking the purpose/result aimed for:

• 忘れないように、メモします。
• I make notes so that I won’t forget.

It is best learned as one chunk:

• verb plain form + ように

Examples:

• 見えるように = so that it can be seen
• 遅れないように = so that one won’t be late

The comma simply separates the purpose phrase from the main statement.

Structure:

• 忘れないように、 = so that I don’t forget,
• 大切なことはすぐメモします。 = as for important things, I write them down right away

The comma is very natural here, but in casual writing it may sometimes be omitted.

大切 is a na-adjective, so when it directly modifies a noun, it takes な.

• 大切 = important / valuable
• こと = thing

So:

• 大切なこと = important things or important matters

Compare:

• 大切です = It is important.
• 大切なこと = an important thing / important things

The な is there because 大切 is describing こと.

Here, は marks the topic or gives contrast/emphasis.

So 大切なことは suggests something like:

• As for important things, ...
• Important things, I...
• At least when something is important, I...

If you said 大切なことをすぐメモします, that would be a more straightforward object marking:

• I write down important things right away.

With は, the sentence has a slight topical or contrastive nuance, as if the speaker is talking specifically about important things.

すぐ means:

• right away
• immediately
• as soon as possible

So すぐメモします means:

• I write it down right away
• I make a note of it immediately

You may also see すぐに. In many cases, すぐ and すぐに are very similar, and すぐ is very natural here.

Yes, essentially.

In everyday Japanese, メモする is a very common verb-like expression meaning:

• to take notes
• to make a note

So:

• メモします
• メモをします

Both are possible, but メモします is very common and natural.

You could also say:

• メモを取ります = I take notes / I make a note

That is another very common expression.

The sentence breaks down like this:

• 忘れないように、 = so that I won’t forget,
• 大切なことは = as for important things,
• すぐ = right away
• メモします = I make a note / write them down

A natural English structure is:

• So that I don’t forget, I write down important things right away.

Japanese often puts the reason, purpose, or condition first, and the main action later.

Not naturally in this sentence.

ように is commonly used when the goal involves:

• ability
• change of state
• something not fully under direct control
• negative purpose like so that I won’t forget

So 忘れないように is very natural.

ために is more often used with deliberate actions and clear intended purposes, but 忘れないために can also exist and means in order not to forget. Still, in everyday Japanese, 忘れないように is often the more natural choice for this kind of sentence.

So:

• 忘れないように、メモします。 = very natural
• 忘れないために、メモします。 = possible, but a bit more direct/formal in feel

Yes. Japanese often leaves out the subject when it is understood from context.

This sentence does not explicitly say I, but the meaning is naturally understood as:

• I write down important things right away so that I don’t forget.

If needed, you could add 私は, but it is usually unnecessary:

• 私は忘れないように、大切なことはすぐメモします。

That is grammatical, but the original sounds more natural unless the speaker specifically wants to emphasize I.

Japanese often leaves out information that is obvious from context.

In 忘れないように, the thing being forgotten is not stated, but the second half makes it clear that it refers to important things or important information.

So the sentence works like this:

• So that I don’t forget [them/those things], I write down important things right away.

Omitting that object is very normal in Japanese.

It is polite overall because it ends with メモします.

However, it also mixes in plain-form grammar where needed:

• 忘れない before ように uses plain form, which is normal grammar
• メモします gives the whole sentence a polite ending

So this is a standard polite sentence, not casual.

A more casual version might be:

• 忘れないように、大切なことはすぐメモする。
• 忘れないように、大切なことはすぐメモするよ。

The original is the kind of sentence you could use in normal polite conversation.