Shin Hisui no Shizuku: Hiiro no Kakera 2 DS

When Suzu's older sister figure Mao suddenly disappears, Suzu is called back to their rural hometown to assume Mao's role as Tamayori-hime — the shrine maiden whose purpose is to sacrifice herself to keep the land safe from the sea lord's wrath. Suzu knows almost nothing about what the role demands. Before she can begin to learn, the sea lord strikes: demons descend on the village, and leading his forces is Toyotama-hime — who turns out to be Mao.