Goat-ish

I think this premise serves a very nice purpose. It shows a handsome yandere acting obsessive in a pretty ace manner. The title is fully serious. The big guy does get very attached to a tiny talking pink doll with a lost soul inside it. He's absolutely (platonically?) in love before the doll regains a human form.

There's a novel. It's available on Manta. I'm not sure how popular this one was but I'm glad I gave it a chance. The layers to the humor genuinely surprised me. The doll, Yuri, eats and loves sweets....and nobody can figure out how he digests food (including him). Yuri is always in the buck because his clothes implode when he changes form, which means most of the "more serious" scenes happen with his cheeks in frame.

If you want to be funny you have to commit. That's my general point.

Mikhail, or Mikey (lol), is an unexpected charmer. A silly insane guy. He was originally meant to be miserable and in love with his secretary, but Yuri is a way better fit for him. Yuri is the type to act cute and play along...and this makes Mikey so happy he doesn't know what to do with himself.

The secretary, Levi, sticks around and does his job. Which is another funny commit to the bit detail. Everybody already knows Mikey is super serious, and one of the most powerful men around. It's easy to see why Levi originally ran away. Mikey (lol) is way too intense. Yuri doesn't mind as much in the beginning because he needs help to survive, andddd then he quickly figures out he likes being spoiled. The opposite of Levi.

Levi is NOT competition. No one ever dares to question or challenge the Duke's love....because he's a known nut.

Yuri’s appearance in isekai world makes everybody's lives better in a more subtle way. Yuri really is a weakling. He's not secretly magical or a holy man or a tactician. He really is a worthless doll, which is yet another commitment to the bit thing that makes Mikey cute and weird.

Yes, of course he goes to balls with his favorite doll in his vest. Why do you ask? Wanna say something about it? Do something about it. I dare you.

Yuri is frequently embarrassed and overwhelmed by his new owner/jailer/roommate...but he always falls in line and stays in the vest pocket.

He is afraid of Mikey for a while, but it's hard to feel bad for him when the Duke is also a little spooked by the talking doll. Especially during their first few days together. Magic isn't super common and dark magic is the highest crime here so there's some mutual jumping around.

When Yuri temporarily pops into human form for the first time it's over. Mikey was already really attached to his annoying, clingy, gluttonous doll. Now that the doll is a cute man he immediately proposes that they become lovers.

The shackles also start coming out more often. Being lovers means dealing with dark magic rumors that could destroy the duchy. Mikey starts to think locking up Yuri would be best....but he always gives in when Yuri says he wants to visit the market and go on dates.

This is the final villain.

Dark magic. You know the drill.

This is Lucky. The dragon Yuri and Mikey have been raising together. Boom.