This is the 9248th most frequent Japanese word.
由実子
"由実子" (Yumiko) is a Japanese female given name, typically meaning "reason, truth, child," though exact meaning can vary based on the kanji used.
In this case, '由実子' is referred to as the recipient of the action described in the sentence.
私は由実子にプレゼントを送りました。
I sent a present to Yumiko.
In this sentence, '由実子' is used as a proper noun, specifically a given name, referring to an individual.
由実子は今日、図書館に行きました。
Yumiko went to the library today.
Here, '由実子' functions as a subject attributing qualities or actions to the person whose name it represents.