Series premieres July 2024. Check out the Crunchyroll article for additional information. Synopsis from AniList:
Naoe-kun, a massage therapist, is about to head home for the day when he’s saddled with a rather strange patient. This lovely lady has emerald eyes, pointy ears, and grew up in the forest–everything about her screams “elf,” except for one thing: her bodacious body. It turns out she left her world but loves junk food in this one, and now her obsession has caught up with her. Can Naoe-kun help this lovable elf girl lose the weight–and keep it off?
I read a portion of the manga a while back and I honestly don’t remember her being more than an occasional side character. Most of the manga centers around the titular elf (blonde on the right). The synopsis describes the MC as a massage therapist, but he often consults these patients as a nutritionist instead, helping them eat better diets (or trying anyway).
Hazy memory spoilers about girl in the back
Iirc, the girl in the back is an oni and he helps her with her diet. I think she was trying to bulk up, but take my memory with a pinch of salt.
Aww. OK sigh.