gakkou no kaeri ni konbini de ocha o katte kimasu.

It means on the way back from school or after school, on the way home.

A very literal breakdown is:

• 学校 = school
• の = linking particle, like of
• 帰り = return, way back
• に = at/on/during

So 学校の帰りに is literally something like at the return from school, but in natural English it becomes on the way home from school.

の connects nouns.

Here, 学校 and 帰り are both being treated like nouns, so の links them:

• 学校の帰り = the return from school
• more naturally: the way back from school

This is a very common pattern in Japanese:

• 仕事の後 = after work
• 授業の前 = before class
• 旅行の途中 = in the middle of a trip

So の is showing the relationship between the two nouns.

帰る is the dictionary-form verb meaning to return / to go home.

帰り is a noun form derived from that verb, and here it means the return trip or the way back.

Compare:

• 学校から帰る = to go home from school
• 学校の帰り = the way back from school

Japanese often uses these noun forms in set expressions like this.

The に marks the time or occasion when something happens.

So:

• 学校の帰りに = on the way home from school
• 帰りに often means on the way back

It works a bit like saying during or when in English.

For example:

• 仕事の帰りに店に寄った = I stopped by a store on the way home from work.
• 帰りに電話してください = Please call me on your way back.

Because で marks the place where an action happens.

Here, the action is buying, and that action happens at the convenience store.

So:

• コンビニで = at the convenience store

Compare:

• 学校で勉強します = study at school
• レストランで食べます = eat at a restaurant

A common beginner confusion is with に. For locations:

• に often marks destination or existence
• で marks where an action takes place

Since buying is an action, で is correct.

を marks the direct object of the verb—the thing being bought.

So:

• お茶を買う = buy tea

Here, お茶 is the thing the speaker will buy, so it takes を.

Other examples:

• パンを食べる = eat bread
• 本を読む = read a book

買ってきます is 買う + てくる in polite form.

Breakdown:

• 買って = te-form of 買う (to buy)
• きます = polite form of くる (to come)

Together, 買ってくる means to go and buy something and come back.

So お茶を買ってきます means:

• I’ll go buy some tea and come back
• or more naturally, I’m going to pick up some tea

The くる part gives the sense that the speaker will return after buying it.

買います simply means buy.

• お茶を買います = I will buy tea.

買ってきます adds the idea of going to get it and then coming back.

• お茶を買ってきます = I’ll go buy tea and come back.

So 買ってきます is more natural if the speaker is leaving the current place, getting tea, and returning.

This is a very important contrast.

• 買ってきます = go buy it and come back toward here / toward the current situation
• 買っていきます = buy it and then go on / take it along away from here

Very roughly:

• くる = come
• いく = go

So:

• お茶を買ってきます = I’ll go buy tea and come back.
• お茶を買っていきます = I’ll buy tea and then head on / take it with me.

きます is non-past polite form. In Japanese, the non-past can mean:

• present habitual
• future

Here it has a future meaning:

• I’ll go buy some tea and come back

If it were きました, that would mean it already happened:

• 買ってきました = I went and bought it / I have bought it and come back

So きます fits because the speaker is saying what they are about to do.

Japanese often omits the subject when it is clear from context.

In English, we usually need I, he, she, etc.
In Japanese, if the situation already makes it obvious, you can just say:

• 学校の帰りにコンビニでお茶を買ってきます。

The listener will usually understand that the speaker means I.

This is completely normal Japanese.

The basic order here is very natural, but Japanese word order is more flexible than English because particles show each word’s role.

This sentence is:

• 学校の帰りに = time/occasion
• コンビニで = place of action
• お茶を = object
• 買ってきます = verb

A very normal pattern is:

time + place + object + verb

You may sometimes see small variations, but the verb usually comes at the end.

お茶 is the normal everyday word for tea.

The お here is an honorific/polite prefix, but in many common words it is so standard that it just feels like part of the word.

For example:

• お茶 = tea
• お水 = water
• お金 = money

You can say 茶 in some contexts, but お茶 is much more natural in ordinary conversation.

Yes. コンビニ is a shortened loanword from English convenience store.

It comes from コンビニエンスストア, but in everyday Japanese people almost always say コンビニ.

This kind of shortening is very common in Japanese loanwords.

Yes, grammatically it could, because きます is non-past and Japanese often relies on context.

So depending on the situation, it could mean:

• I’ll buy tea at a convenience store on the way home from school.
  or
• I buy tea at a convenience store on the way home from school.

But in many real-life situations, 買ってきます strongly sounds like something the speaker is about to go do now: I’ll go buy some tea and come back.

Context decides which reading is intended.