I feel like the end game here is just him turning back into a human but still being treated like a dog by Inukai. Maybe as payback for all the embarrassing stuff he's seen and done so far, but by then he's developed a taste for this anyway.
She did what to her dog I can't believe there's actual plot backing this (or well, at least that's what we're supposed to believe for now).
"Boy turns into dog after the mysterious experiment of a girl at his school" sounds even less believable than just plain simple "Boy wakes up as dog" though.