The guy is just scared, he is literally a slave depending on her for everything and the other guy is a freaking prince. At the end of the day, the big "betrayal" is just him bringing back a (supposed) lost girl back to her family, and then he literally died to save her life. He surely didn't act like the best boy but it's not like he imprisoned or tried to kill her, yandere has nothing to do with what is happening here. People decide to judge a story Reading spoilers and not even understand them.