The Dragon's Soulmate is a Mushroom Princess! novel volume 4 was written by Hanami Nishine with illustrations by poporucha.

Agnes and Claude have been preparing for their wedding since returning from the Kingdom of Oreille, when they receive troubling news about the Hole in the Wall growing bigger while they were away. Agnes learns this hole is where monsters come from and has been maintained by the Oreillian and Visage royal families for generations. Having learned of the ancient duty of the dragon-blooded Visage Royals, Agnes begins to wonder about her own role as a descendant of Oreillian royalty and what she can do to help. Gathering her courage, Agnes and Claude head to seal the problematic Hole in the Wall before their long-awaited wedding. Overcoming hardships with the power of mushrooms is a staple of this completely mushy-mushroom romantic comedy!