Koori no Mamono no Monogatari Gaiden

Overview

In the beginning, there was a demon in a cave: Blood, trapped in ice for many decades. In order to break the curse that bound him, he searched for the "tear jewel". One day, a youth called Ishuca appeared before him. He was suffering from an illness, and had come to the cave to die. Blood was touched by Ishuca's kindness, and began to feel drawn to him. However, death soon came to Ishuca, and, saddened by the death, Blood began to weep. His tear became the "tear jewel", and Ishuca's life was saved through its power. The two set off on a journey. On the way, Blood was reunited with some old companions, but - since the demons wanted him to return to his old self, and Blood wanted to continue to travels with Ishuca - his former companions became his enemies. Upon confessing his own past to Ishuca, Blood promised never to kill another human. Having completed their journey - and with the aim of finding the jewel that Wild, the jewel-dealer, had asked for - they find themselves at the Toei Cliffs...!?

Source: AniList