Wataru Kasasagi

Watase's elder twin sister. Deceased. Age 16 at the time of death.
A girl who valued life and lived her own life actively and positively.
Thus she deemed saving lives to be the highest form of righteousness and aspired to be a rescue worker. However, her young life came to an abrupt end after she saved Watase during the Great Rokumei City Arson.
Her proactive mindset and way of life had a huge impact on Watase and was the biggest driving force in making him abandon his inactive lifestyle to become a rescue worker.

From in-game TIPS