Board Thread:News and Announcements/@comment-99.165.44.227-20200222001748/@comment-45973512-20200812032410

Pretty sure Krul Tepes mentioned that the only Hyakuya children that survived was the children in the orphanage that got spared. The rest got anihilated by her. That said, since the predecessors of the Japanese Imperial Demon Army were the rivals of the Hyakuya sect, they probably had the means to do their own Seraph expirements.

Edit: Mb. She actually did get expiremented on by the Hyakuya Sect and not the JIDA. Mahiru provided Guren with the details beforehand. Though this does go back to the original question. It might have something to do with her Seraph factor inside her body. I guess either Guren or the JIDA had something to do with her getting infected.