You were in tenjiku for a long time, you haven't really noticed but izana has grown a liking towards you. Maybe too much, he haven't shown signs of it. He was really good at hiding things, including his obsession towards you.

Is that too much? well it's going to be worse from then on.

His obsession started growing every day, he may or may not be a yandere for you. When he sees you talking or standing near anyone except him he gets jealous really fast.