Bad events are how most famous yanderes are made.
I just hope there is a dynamic change to a character in this story that will stay it's what I will try to make happen, but they like NOPE not going to let you and then I will cry. Preferably I like the bad and good changes but I prefer bad first. Also all the build up to the change of Tsubaki was all wasted, but I have enjoyed the story, still disappointed sadly.
No human can judge a human heart so what may seem pure could not be.