An Arven from Pokémon Scarlet and Violet? I could definitely see his weight spiraling, his uniform getting too tight everywhere, with Nemona as comparison/support trying to help him lose weight, yet failing hard, and in denial about getting any heavier.
HOOOOOH OH YEAH I LOVE THIS IDEA!!!!
What if after they graduate some years in the future from the academy they move to the same apartment together? Nemona continues her journey of becoming the best at Pokemon battles, whereas Arven begins his culinary journey, with the goal of becoming the best chef in Paldea!
Now, who else but yourself to test out your own meals? There's no academy or other obligations to really worry about, so I can imagine Arven gets so invested in making meals and trying all of them, spending most days inside the kitchen, that his body begins packing on pounds with a speedy pace.
Nemona definitely notices, Arven doesn't, and if he does, he just passes it as some minor bloating, even if he's managed to push through 400 pounds with ease. Nemona herself isn't the type to shamelessly call out his weight. Hell, maybe she thinks this is just a phase and he'll plateau eventually, right?
But he starts to get alarmingly obese, and not an ounce of him hints at the idea that he's planning to diet anytime soon, so she tries her best to help his friend out and gives him indirect conversations about his weight and recommendations to become healthier. Arven, however, denies everything and gets confused at all of her attempts to insinuate he's "packing some extra weight" or "causing the floorboards to creak". It's been a couple years since he's begun focusing on his cooking, and now he can't resist devouring everything he makes! That's a win for a chef, is it not?
Maybe he's completely unconscious of the extreme weight gain he's going through. He still goes out to buy ingredients himself or to do other activities after all, but his legs and back are constantly aching, much to his confusion.
He's already nearing the 800 pounds milestone, and Nemona's still trying her best to get Arven down a healthier path before it's too late.
Tada! Let me know what you think :3c
