Fenrir?

After the summoning class ended, the students began making their way back to the class, their summoned familiars having returned to the Astral World. It was a necessary process since their magic power wasn't yet strong enough to sustain the presence of their familiars in this world for long. The exception to this rule was Titania, who had chosen to remain in her smaller form to conserve Leo's magic.

As Marcus strolled through the academy halls, the black wolf remained in his arms, its fur soft and warm. It was strange. The wolf hadn't returned to the Astral World like the others, and what was even more perplexing was that Marcus couldn't feel any drain on his mana. Familiars normally required a constant supply of their summoner's magic to stay in this world, but this wolf seemed different.

Marcus's brow furrowed in thought. Why is this wolf not returning?