He was part of the last pockets of human survivors during the great war. While exploring with his team, they ran into something they couldn't identify—and things went bad fast. Riku, who was leading the group, made the call to have him sacrifice himself so the rest could make it out alive.
He's Nonna's father, though his actual name isn't clear from available records.
Content compiled by AnimeList.moe from publicly available sources.
