Genjitsubanareshita Bishoujo Tenkousei ga, Oya no Kimeta Doukyo Aite de Komaru

High school boy Iriya Takeru is enjoying living on his own, as the fourth son of a prominent family...

"What am I going do?"

Due to her parents' circumstances, his fiancee ends up moving in to live with him!

"I can cook and improve your diet."

"I'll also take care of the cleaning."

"Isn't it more convenient with two people?"

Takeru thought his fiancee, Amamiya-san, would be a sheltered young lady, but she
turns out to be "willing to do anything" to take care of him.
At school, she is revered as the perfect young lady, but
at home, she is a devoted doting partner. A youthful romantic comedy
between a self-indulgent young man and a caring young lady,
living together as a frustrating duo.

(Source: Fantasia Bunko, translated)