Your Long Hair in the Wind

Goro is Izumi's step brother. They're really close to each other, but there's a secret between them. On their childhood, Izumi's long hair had been cut by Goro without knowing the reason. Since that day, Izumi never let her hair get longer again. Why did Goro cut his sister's hair? Does he hate it? And what will Izumi do to open Goro's heart about this problem?