kono otya ha watasi ni ha sukosi nigai desu ga, haha ha suki desu.

They are doing two different jobs.

• このお茶は sets this tea as the main topic.
• 私には is に + は, and here は adds contrast or emphasis: for me / as far as I’m concerned.

So the sentence is not just saying something about the tea. It is saying:

• As for this tea, for me, it is a little bitter...

That contrast is important, because the next clause shows that someone else feels differently: 母は好きです.

Here, に marks the person who experiences the taste or judgment.

With words like 苦い, Japanese can describe how something feels to someone:

• 私には苦い = It is bitter to me / I find it bitter
• 子どもには辛い = It is spicy for children
• 私には難しい = It is difficult for me

If you said 私は少し苦いです, that would sound like I am a little bitter, which is not the meaning here.

So 私には is used because the tea is bitter from my point of view.

には often adds a sense of contrast, something like:

• for me
• to me
• at least in my case

So 私には少し苦い suggests:

• I find it a little bitter
• maybe but others might not

That matches the second half of the sentence, where the mother likes it.

Without the contrastive は, the sentence would lose some of that “as for me” nuance.

Because 苦い is an i-adjective.

For i-adjectives, the polite form is simply:

• 苦いです
• おいしいです
• 高いです

You do not add だ after an i-adjective.

So:

• 苦いです = correct
• 苦いだ = incorrect
• 苦いだです = incorrect

少し means a little or slightly.

It modifies 苦い, so:

• 少し苦い = a little bitter

It also softens the statement. Saying something is 少し苦い sounds gentler than just saying 苦い.

This kind of softening is very common in Japanese.

In this sentence, が means but and connects two clauses:

• このお茶は私には少し苦いです
• 母は好きです

So the whole sentence sets up a contrast:

• I find this tea a little bitter, but my mother likes it.

This use of が is very common in Japanese for a softer, more natural contrast than a strong English-style but sometimes feels.

Because Japanese often leaves out information that is already clear from context.

The topic このお茶 has already been introduced, so in 母は好きです, the thing the mother likes is understood to be this tea.

A fuller version would be:

• 母はこのお茶が好きです

But once the tea has already been established as the topic, Japanese often omits it.

This is a very common point of confusion.

In Japanese, 好き is not a regular verb. It behaves like a na-adjective.

So instead of saying something like mother likes, Japanese literally uses a structure closer to:

• As for my mother, this tea is liked

That is why you often see patterns like:

• 私は犬が好きです
• 母はコーヒーが好きです

So 好きです is the normal and natural way to say someone likes something.

When talking about your own family members, Japanese often uses the plain family term without 私の.

So:

• 母 = my mother in this kind of context

Adding 私の is possible, but it is often unnecessary if the meaning is obvious.

This is very common with family words:

• 母 = my mother
• 父 = my father
• 兄 = my older brother

By itself, yes, it would need context. It could feel incomplete because 好き usually needs something that is liked.

But in this sentence, the topic このお茶 has already been established, so the meaning is clear:

• As for my mother, [she] likes it

This kind of omission is extremely common in natural Japanese.

Yes, it is natural and understandable.

A speaker might also say the more explicit version:

• このお茶は私には少し苦いですが、母はこのお茶が好きです。

But that sounds more repetitive. The original is more natural because Japanese often avoids repeating things that are already understood.

So the sentence is a good example of:

• topic marking with は
• contrast with には
• clause connection with が
• omission of understood information in the second clause