The Replacement ( Number Five Story)

When Ben passed, Hargreaves believed that number six needed a replacement. When she was Introduced to the rest of the academy, no one liked her except vanya.

Five was already gone. Year by year the kids left the academy. 10 years later Hargreaves passed away In his sleep.

Five comes back with world ending new and need every one to help. He didn't know that number six got a replacement. How does he react?