Tondemo Knight by Rie Kosaka

Romantic comedy. Kanna's overprotective father has built a guardian android for his daughter in the image of his younger self, dubbing it the "Miracle Superhumanoid Papa Protector" (a.k.a. Yashiki Kojiro). A strange design flaw causes Kojiro to lose his head when he experiences overwhelming emotions.

Shoujo manga for sale at Mangaroo.