This is the 3413th most frequent Japanese word.
浩一
"浩一" is a Japanese given name, typically male, meaning "vast" (浩) and "one" (一).
In this sentence, 浩一 is used as a proper noun referring to a person's name, indicating an individual identified by this name.
浩一は優しい性格の持ち主です。
Koichi has a kind personality.
Here, 浩一 is specifically identifying the subject's name, functioning as an individual's proper name within the sentence.
彼の名前は浩一という。
His name is Koichi.
In this case, 浩一 is used in the context of addressing someone directly, followed by the honorific 'さん' for politeness.