約
This Chinese character means promise.
You can watch how to write this. - (「約」の書き順（筆順）動画 - 漢字書き順辞典)
This Chinese character is read as "やく".
For example, "約束 (やくそく)" means promise.
"約" has another way to use.
For example, "約百人 (やくひゃくにん)" means "about 100 people".
"約" means about in this context.
For now, please remember "約束" and the meaning as "about".
Do you know The Promised Neverland?
The Promised Neverland is "約束のネバーランド" in Japanese.
By Higashi-Mikawa Kyōjindō Shujin (東三河狂人堂主人)