Rein started Anneshia's treatment immediately. She was very careful with the way he handled all that. He did his best to control the power of his soul damaging attacks as much as possible to just lightly injure Anneshia's soul.
But if he kept on being so cautious then this process would still end up taking a lot of time. For that reason Anneshia herself asked Rein to speed up the process. Rein was really unwilling to do so as he had very little experience dealing with souls.
But as Anneshia was fine with it he did start to increase the amount of power he was using and the damage he was dealing also increased. But the danger to Anneshia's life did not as her broken cocoon break ability was still just as strong as it was before.