Cold-Hearted - Taiyou X Reader (oneshot)

This is an I.E oneshot. The reader used,yes,used,to be a cheery,friendly,kind girl. But ... because of a certain incident and because a person who was precious to her was involved in that certain incident,she wasn't the bright girl anyone knew already. Instead,she was cold and very nasty. What happens if a certain boy melted her cold heart? And who was that certain person who died in the incident? (Please be informed the Taiyou in this story is already out of hospital)