Usually if the story ends because the couple finally confessed to each other, it's because the author's understanding of a romantic story is infantile. Dating is hard work and serious effort, and the process itself can create complex stories that are absolutely worth telling. (It has it's faults but Horimiya URL:
https://mangadex.org/title/6770/horimiya is an example of this.)
The fact that this story dragged its feet to end at a confession is simply confirmation that this author doesn't know enough about people to tell a story about them.
If you want to see this story written by someone with a more solid understanding of human beings, and are willing to deal with a less extensive art style consider this manga:
Yandere Kanojo
https://mangadex.org/title/489/yandere-kanojo
https://mangadex.org/title/23307/yandere-kanojo-online
P.S. the Yan comes from Yankee, as in delinquent, not Yan as in mentally sick, so the Yandere is not the one we are used to.