に is a particle that marks a noun as being a target.1

Example: I throw a ball to/at Akari

γ‚γŸγ—γŒγΌγƒΌγ‚‹γ‚’γ‚γ‹γ‚Šγ«γͺげる

Info

In this example, γ‚γŸγ— (I) is marked by the が particle making it the core subject of the sentence.

γ‚γ‹γ‚Š (Akari) is marked by に which makes her the target of the action.

γͺげる (throw) is the action.

Footnotes

  1. Japanese from Scratch (3) ↩