By accident, she had a romantic relationship with him, and he left a note telling her to wait for him and that he would marry her when he came back. She waited for him for ten years and saw him become the number one person in the Purple Void Realm.
He forgot, forgot his words, and yes, there was nothing worth remembering about a one-night stand. Everything was just her wishful thinking.
This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.