karee ha sukosi karai keredo, oisii.

は marks カレー as the topic of the sentence.

So カレーは means something like:

• As for the curry,
• Speaking of the curry,

The sentence is then making comments about that topic: it is a little spicy, but delicious.

This is different from が, which often marks the grammatical subject more directly. In a simple sentence like this, は sounds very natural because the speaker is talking about curry as the thing under discussion.

少し means a little or slightly.

So 少し辛い means:

• a little spicy
• slightly spicy

It softens the adjective 辛い. Without 少し, 辛い would simply mean spicy.

The readings are:

• 少し → すこし
• 辛い → からい

So the sentence is read:

カレーは すこし からい けれど、おいしい。

辛い is an い-adjective, and here it finishes the first clause:

• カレーは少し辛い = The curry is a little spicy

Then けれど connects that clause to the next one:

• カレーは少し辛いけれど、おいしい。
• The curry is a little spicy, but it’s delicious.

In Japanese, い-adjectives can end a clause by themselves, so you do not need a word like is after 辛い.

けれど means but, although, or though. It connects two parts of one sentence.

In this sentence:

• 少し辛いけれど、おいしい
• It’s a little spicy, but delicious

でも also means but, but it is more often used at the beginning of a new sentence or statement:

• 少し辛い。でも、おいしい。
• It’s a little spicy. But it’s delicious.

So けれど is more of an internal connector, while でも often feels like starting a separate sentence.

Japanese often omits things that are already understood from context.

In:

• カレーは少し辛いけれど、おいしい。

the second part does not repeat カレーは, but it is still understood:

• (カレーは) おいしい
• (The curry) is delicious

In English, repeating the subject is usually required. In Japanese, it is usually omitted if it is obvious.

This sentence is in a plain style form:

• カレーは少し辛いけれど、おいしい。

If you want to make it more polite, you can say:

• カレーは少し辛いけれど、おいしいです。

Or even more balanced:

• カレーは少し辛いですけれど、おいしいです。

All of these are natural, but the original sentence sounds casual or plain.

Yes, it can.

Japanese speakers sometimes end a sentence with けれど or けど and leave the rest implied. This can sound softer or less direct.

For example:

• 少し辛いけれど…。
• It’s a little spicy, though...

That might imply something like:

• ...I still like it
• ...maybe not everyone will enjoy it
• ...what do you think?

In your sentence, however, the speaker actually finishes the thought with おいしい.

Yes. おいしい is also an い-adjective.

So both of these are adjectives:

• 辛い = spicy
• おいしい = delicious

That is why the sentence can work without a separate word for is:

• カレーは少し辛い。
• カレーはおいしい。

Japanese い-adjectives can function like complete predicates.

The comma helps show a pause:

• カレーは少し辛いけれど、おいしい。

It makes the sentence easier to read and reflects the natural spoken rhythm:
It’s a little spicy, but delicious.

Japanese punctuation is somewhat flexible, so you may sometimes see similar sentences with or without a comma. In this case, the comma is very normal.

Yes. けれど can often be translated in several ways depending on context:

• The curry is a little spicy, but it’s delicious.
• Although the curry is a little spicy, it’s delicious.
• The curry is a little spicy, though it’s delicious.

The basic contrast is the same: spicy and delicious are being presented together, with a slight contrast between them.