Houkai Gakuen 2 - Sin Mal/Comic

Sin Mal (comic) set in months before the X-10 Experiment (2013) when Sin was originally a child in wealthy merchant family. Various incidents happened changed Sin from a docile and happy child into a sadist and burned her whole house, later becomes an orphan and seeks to Cocolia Orphanage.

Link: Alternative Official Raw - Weixin (Last chapter, Has links to other chapters at the bottom)