Grammar Point
particle
prt 
に

because of (reason), for, with

Noun + に

An indirect object marker. The particle に can be used to indicate the reason or cause for a certain emotion or physical reaction. It marks the specific thing that triggers the response.

Noun + に + Verb

In this construction, the noun represents the cause or reason for the action or state described by the following verb.

I was surprised at the news.

I was troubled by the noise.

Note

This usage of に is often used with verbs that express emotions like surprise, disappointment, or joy. It can also be used with nouns that describe physical states like being wet with rain or smelling of something.

Words: 
に
Radicals of radicals