Grimmjow

Based on your description, the anime you are looking for might be "Orange." It aired in 2016, which falls within the timeframe you mentioned. "Orange" tells the story of Naho Takamiya, a high school girl who receives letters from her future self. The letters instruct her to prevent the regrets of her new transfer student classmate, Kakeru Naruse. The story revolves around Naho and her friends trying to change the future and save Kakeru from a tragic fate. The romantic aspect between Naho and Kakeru, as well as the theme of past lives and second chances, align with the details you provided. The side story you mentioned about the lady waiting for her husband might be the subplot involving Hiroto Suwa, one of Naho's friends, and his connection to another classmate named Rio. The cliff monument you referred to could be related to this storyline.

Thought i might as well post something

For those who haven't watched yet deffo give it a watch https://myanimelist.net/anime/269/Bleach