>>280504078
It's very subtle but you can definetely tell how Hei changes thought the season and how focused on Yin he becomes, from the way he looks at her or how he risks his life to protect her. It's very notable in the episode where he helps a guy who's in love with a doll. Hei projects himself onto him and hopes to get some answers. Hei then helps them run away together do they can live a normal life.