But she spared him and yes Koharu-chan, she killed her unintentionally. Nana originally want the twins to escape as if she was killed to deceive Tsuruoka but you know... This bastard Tsuruoka shot Koharu-chan first, ordered Moe-chan to killed her and because Nana remembered Moe-chan grandmother message, she killed her instead.
No buddy, the sacrifices that I talking about is when Michiru-chan sacrifices her life to revive Nana from dying. And killed the twin girl? Well you know.. Tsuruoka is dirty sly human who forced Nana to kill Koharu-chan. She remembered about Moe-chan grandmother that said please don't let her astray, so she killed Koharu-chan unintentionally. She didn't want Moe-chan dirty her hands.
That's because Hinata never really had any attachments towards others except for her original family and Sasae loves his current family so when he saw that Hinata finally made a friend and is happy with her he just can't bring himself to hurt her.