Explanation for the plot twist (under a spoiler cut):
Rino is the reincarnation of a character from Peach Boy Riverside, Cool's old webcomic (which is currently getting a "One Punch Man" remake with Yohane as the artist). Rino's servants and Nozomu's mother also appeared in that comic.
I did not expect this manga, especially because it was a spin-off, to be this good. Yeah, it was pretty rough around the edges in some parts, especially the pacing, but the story, characters, and comedy were FAR above what I had expected. The slice of life 4-koma -> serious pages -> 4-koma again was a neat idea, and pulled off really nicely. All in all, I'd say this manga is definitely worth reading. It's a good manga with a satisfying conclusion. 10/10, would read again, all hail legal-lolis!
@Karkeys Honestly, I couldn't have said it better myself.