Woof Woof Story: I Told You to Turn Me Into a Pampered Pooch, Not Fenrir!, Vol. 4 (light novel) - Inumajin - Bog

Well, everyone saw this coming...With an appetite fit for the King of the Fen Wolves, it was only a matter of time before Routa grew too big for the mansion. This dog needs diet and exercise! ...Okay, that's too much effort. Thankfully, there's more than one way to achieve a smaller form, and he knows just who to turn to for a lesson in shape-shifting! But as the full moon rises, Routa soon learns that a battle with weight loss isn't the only challenge headed his way-Carmilla, haughty vampiress and a general of the Demon Lord's army, takes the stage! And she's got her sights set on Lady Mary!