Red Spear

While training in the mountains, Itsuki is attacked by a larva, a magical creature that makes nightmares reality, and is saved by Sekiren, a traveling member of Astral. On Itsuki's request, Sekiren trains him in martial arts. In a break in training, Sekiren visits Astral and asks Nekoyashiki to allow him to take on a mission offered to Astral.

Synopsis excerpt via Kitsu.