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"Fuyuyami Hoshizora, after eavesdropping on Natsuki Subaru and Emilia's heartfelt moment, decides against leaving Roswaal's Manor. Perhaps there is another way to survive, one that doesn't involve breaking Subaru's heart."
The First IF route planned for this series, splitting off from the main timeline during the events of Arc 2. Along with being titled as the "Diligence IF," it can also be referred to as the "Obsession IF."
Why?
Well, just as a warning for you all, it wouldn't be correct to say that these virtue IF stories are happy endings. Much like the sin IF stories from the original series, these are meant to be bad iterations of the main timeline. However, I will not explain how they are considered to be such.
Thus, you can infer that in these timelines, Fuyuyami Hoshizora goes too far while trying to be virtuous. He steps past the boundary of virtue and into the realm of vices.