Their Winged Popsicle (read desc)

Long ago, even before Sukuna, there wasn't war, just peace, until some scientists decided it would be fun to make a DIY weapon. The main lab where the scientists had been working suddenly disappeared, but was later found in ruins on the island it had been located. This caused issues that were easy to fix for the humans. Just built another. No. The facilities continued disappearing to unknown forces.

Aight, so this book's gonna have a sort of love triangle-or love square in a way, but mainly a love triangle between Whiteout, Sukuna, and Yuji

Whiteout: A secretly broken woman with a ton of trauma. She only has a few people who know of her past, and she barely sees them anymore. She's really good at hiding things and putting on a mask, along with forgetting stuff temporarily and sleeping whenever wherever.
Her eyes are sapphire blue with diamond shaped pupils, although her pupils only change shape when she transforms. She's 7'2" in human form, 10'8" in hybrid, and 8'9" in full dragon form.

(Aight, so, I sorta took season 1 - 3 and shifted it how I wanted, as one does. This is like my first book (that isn't does yet, but I got inspired to I started this one-that and I love JJK) that's called From a Myth To Reality. That one is One Piece based though, with Whiteout and Katakuri.)