That relationship went so fast. I mean, she literally tells him to come in her home when they met the second time and then he spends the night there. The romance is too fast.
Truth is, he didn't actually spend the night at her place! In the manga, the author draw a small pic/scene where it shows he woke up when she got out of the bath and went straight home in the blank page between the two chapters. But the scans don't show the pages between the chapters so... ╮( ̄▽ ̄)╭
All these years that winter has been experimented by Sara, no one has ever stood up against that woman with a warning except for Jane. Jane is truly precious and pure.