The に particle is a difficult particle to master because it has so many uses. We’ll only take a look at a couple of uses for now, but when we get to the advanced stage of grammar, we’ll talk more about に. In the general sense, you use に when you want to indicate toward who or what the action of the verb is directed to. For example, に can indicate the goal toward which things move. For example in the sentence なごや に いきました would mean “I went to Nagoya”. (なごや = Nagoya. に = ni particle. いきました = went.) Here the に particle takes on the meaning of “to”.
Now take a look at a sentence like this, そふ に てがみ を かきました which means “[I] wrote a letter to [my] grandpa”. (そふ = grandfather. に = ni particle. てがみ = letter. を = wo particle. かきました = wrote). Here the に also means “to” but it’s not used in the sense of direction or place like the example used in “I went to Nagoya”, it’s used as an indirect object marker. Take a look at another sentence, せんせい に しゅくだい を さしあげました which means “I gave the homework to the teacher”. (せんせい = teacher. に = ni particle. しゅくだい = homework. を = wo particle. さしあげました = gave).
The example, “I gave the homework to the teacher” is similar to the example “I wrote a letter to my grandfather”. Now we’ll look at another usage for に that is entirely different from the three examples we used. Take a look at a sentence like this, どうようび に ながの に かえりません which means “[I] will not return to Nagano on Saturday.” (どうようび = Saturday. に = ni particle. ながの = Nagano. に = ni particle. かえりません = will not). Here there are two に particles. Let’s tackle the second に particle that appears in the sentence. The second に serves the function of indicating the goal of movement.
However the first に serves a different function. The second に serves as a time indicator. In this example, どうようび was the specific time indicator. The same goes for this sentence, しちじ に たべます or “[I] will eat at seven o’clock”. (しちじ = seven o’clock. に = ni particle. たべます = will eat.) Here しちじ was the indication of time. Now there are certain time expressions in which people don’t normally use に. For example, words like きょう and あした are not followed by に. (きょう = today. あした = tomorrow) However, some people do use に after words like あさ and よる. (あさ = morning. よる = night.)