Mahou Tsukai no Yome - Nishi no Shounen to Seiran no Kishi OVA - 03 (last)

The Wild Hunt, a group of fae knights on horseback, awakens every few decades and wanders the land. Their presence brings change to the vegetation, causing old plants to wither and new ones to flourish. However, when the stone monument housing the Wild Hunt is struck by lightning, a fragment containing the group's guide is chipped off. This causes the knights to lose their formation and wander aimlessly, leaving destruction in their path. To solve this issue, Spriggan assigns Elias Ainsworth the task of retrieving the missing guide's horse and returning it to its rightful owner. Meanwhile, Gabriel, a young boy with a thirst for adventure who suffers from asthma, comes across the chipped-off rock and accidentally summons the knight inside. With his memory limited to the desire to reunite with his pack, the guide must find his horse and regain his place within the Wild Hunt before their unorganized roaming causes permanent damage.