Those who don't play Kingdom Hearts but have a vague knowledge of the games know that the lore for the games is infamously convoluted. This OVA is no different. At the very least, it's not outsider-friendly.
For those who don't know, this OVA was based on some key moments from the mobile game "Kingdom Hearts X Dark Roads". There's a lot of context that's missed in this OVA. This is because a lot of the context that comes from the phone game is stuff that happens from the perspective of the player character. Some of the moments in the OVA were flashbacks in the game while other parts in the game were happening "in real time".
The OVA also doesn't reflect the full story of KHxDR. Obviously, it can't because the phone game has hours of content. Because of that though, there's a handful of loose threads that don't have satisfying answers.
It's for these reasons I wouldn't recommend non-fans of Kingdom Hearts giving this a watch. I think the only positives an outsider would be able to appreciate would be the fight choreography and the character designs.
As a Kingdom Hearts fan though, I liked the OVA. And I definitely would recommend watching this to other KH fans. It was really cool to see some of my fav characters from the phone game reanimated with full 3D models and fully voiced.