Help his mother out.

"So... See, my Mom is a big stress eater, and she's grown insecure about her body as she put on weight..." Izuku started slowly.

"Oh? Does Master want to get with his mother? Naughty, naughty!" Momo teased.

"No, nothing like that!" Izuku blushed heavily.

"It's fine, Master. The only reason **** is inherently wrong is because of potential genetic consequences. But by that logic, we should ban all people with inheritable genetic problems from reproducing, and that's just eugenics at that point. Besides, I can easily remove potential genetic consequences, or prevent pregnancy altogether! So it's really up to you if your own inhibitions keep you from going there."

"Gah, just no!" Izuku protested. "Look... I just want you to see if you can restore her to a weight she would prefer, and a healthier one at that. Considering it's my fault she developed unhealthy eating habits, I want to fix the consequences..."

"Your fault?" Momo asked.

"It's a long story. She just worries about me a lot, you know?" Izuku rubbed the back of his head. "...can you do it? And do it in a way that won't raise any eyebrows now that I think about it?"

"Of course Master! I can bring her back to a sexy body, and make sure no one besides you remembers her ever being overweight!" Momo replied. "I can even change all records and photos to reflect the new reality!"

"...alright, then do it," Izuku nodded. "I wish for that to happen."

Momo's eyes glowed red as she accessed her repository of cosmic power and knowledge, locating Inko Midoriya, all people who remember her gaining weight, and all records and images that reflected it. She snapped her fingers, releasing the power, changing Inko back to the body she had before she started stress eating, minus the fact she was a little older now, and all photos and medical records and I.D details changed to match. Furthermore, neither Inko nor anyone who knew her well enough would remember her ever being overweight.

Izuku checked his phone after several seconds, and stared in shock as he watched family photos he scrolled through changing completely. "...so, believe me now, Master?" Momo asked.

Izuku gulped and nodded, his mind racing with the possibilities. It was all overwhelming.

(Note: I don't actually intend to take this particular route down an **** path. This was just to establish Izuku caring about his mother and using Momo's new power as his first act without personal gain. He's a cinnamon roll like that. However, it certainly opens up the possibility of an **** branch, which I may well do if enough people ask for it, or at the very least, someone else can write it if they like. I certainly don't mind **** in fictional erotica, but I also know some people do.)