Zhang Yi and Xiao Yin are two people with completely different personalities, at least when they still spend time together.
Zhang Yi is enthusiastic and has the enthusiasm of a teenager.
Xiao Yin endured it and always sat in the corner of the classroom.
Maybe it's because Zhang Yi has a character that Xiao Yin never had, or maybe it's because Xiao Yin accepted that warmth in a self-righteous way.
So the warmth like the warm sun turned into lava, rolling and burning through those years.