Rule Ihan wa Iku made H!?: Osananajimi to Doukyo hajimemashita

Yuki decided to live alone when she got a job.

However due to a mistake in the contract she has to live with Keita, her childhood friend!

The two of them then established a set of rules for their cohabitation life together but there's a penalty if one break the rules!

What's the penalty?!