She's always depressed of how her boyfriend acted towards her and how he's being so over protective. So, the only way for her to avoids him from "taking care" of her is changing her phone number and move away from where she live now.

Minwoo (T.K) was a very dedicated boyfriend. He had this tradition of writing letters for you every day but handed them to you at the end of the year. The surprise was bigger this year though, as the last letter contained his most precious feelings towards you.