Steven Universe The Pillar Man (JJBA x Steven Universe): Steven is kidnapped at a young age and is found and raised by the Pillar Men, consisting of Kars, Wamuu, and Esidisi

The Useless Devil (BNHA x JJBA): Deku is born quirkless and he doesn't really have a father figure in his life. So when he answers a phone he finds on the ground, he finds that he can just skip ahead of everyone

Naruto The Vampire (JJBA x Naruto): Naruto finds a stone mask and puts it on, how will this end for him?

Lily and The World Over Heaven (JJBA x TLH): a 16-year-old Lily Loud finds that she can manifest a spirit... a very powerful one at that.

Naruto and The World (JJBA x Naruto): Naruto is shot with an arrow and finds that he has somebody following him, a man that looked to be made of gold.

Steven Kujo (JJBA x Steven Universe): Instead of Greg being Steven's father, it's Jotaro Kujo, and Steven has a stand!

Deku: The Pillar Hero (JJBA x BNHA): Deku thought he was quirkless, but he isn't. When he accidentally 'absorbed' someone, he decides to run away from home

Maroco and Star Platinum (JJBA x Star vs The Forces of Evil): Marco slowly realizes that his reappearance in Mewni is destroying his life on earth. But if he stays, things will get worse. But things only get harder, when he decides to run away with the help of his Fighting Spirit.

Uzumaki of Hamon (JJBA x Naruto): Naruto, cold and alone on the street, is found by an old man.

Hamon Rocker (JJBA x TLH): Luna, while searching for her brother, is attacked by a bunch of men. But she is saved by a man with a cool top-hat.

Full Jojo House (JJBA): Kira just wanted to live a normal life. So when a bunch of people shows up in his house for no reason and they refuse to leave, he begrudgingly allows them to live with him (For the explanation, watch this)

https://youtu.be/9ZlNmBM8K3Q