I caught up on Dai Dark recently, and given that I have abdl brainrot I kept thinking about how I could include diapers into it which ultimately led to me making this OC. His name is Nyūshino Shō and here's some facts about him:

Profession: Xeno-Archeologist/Treasure Hunter
Species: Creature of Darkness
Height: Variable
Temporal Age: 32
Physical Age: 8-11
Favorite Food: Claims it's Misetani's boozy manju buns, but it's actually loaded nacho burritos
Favorite Color: Blue
Likes: Misetani Box, Chōyēji, exploring, frogs, sleeping in, diapers
Dislikes: bright light, people who lack manners, changing his own diapers, haggling

As a consequence of his chosen profession, Sho spends a lot of time traveling to different planets in search of the ruins of long extinct alien races and cultures. In his explorations he discovers ancient artifacts and technology—along with rare and ancient bones—and on one of these trips he discovered a strange but well preserved artificial organ. This organ, once implanted and connected to a person's lymphatic system, allows a person to change and manipulate their physical features at will, including their perceived age.
Another piece of technology he discovered in his travels is a sentient biotech frog—named Choyeji—that he developed a close friendship with and who acts as his paggy.

Sho is utterly smitten with Misetani Box, and as a consequence is easily scammed by her! The two of them have a special relationship in which he buys diapers from her and is also pays for a special subscription service where Misetani will change his diapers whenever he rings for her.
The first time he bought diapers from her she offered him the service by giving him a free trial, and he was immediately hooked due to how thorough she was.
While Sho has a massive and helpless crush on her and opens himself up to being scammed by her; on the flipside, it's unknown how Misetani feels about him, she certainly seems warmer with him than she does with anyone else. The fact that she offered him a service where she changes his diapers certainly seems out of character, so it could be that she's just a pervert for diaperboys. She also doesn't scam him for nearly as much as she could given how infatuated he is with her, so that could be construed as her being fond of him given that she wouldn't extend that grace to anybody else.

Art Notes:
I made his head a bit too big proportionally here, so he looks a couple of years younger than he should