I don't remember much but it was a anime where a guy loses his card due to an explosion and no longer can use fuse with a supernatural being for powers.
But this girl finds his card and now he can have that ability again.
This sounds a lot like Luck and Logic, an anime in which the main characters must fuse with spirits called "Logic" named after various gods/goddesses/deities in order to fight evildoers from a different planet, called "Outsiders". Their "Logic" is held on cards that allow them to perform the fusion.
Specifically, the main character Yoshichika Tsurugi is a character who once was a very powerful Logicalist, who loses his Logic some time before the story begins in a desperate attempt to save civilians and destroy a powerful Outsider. His sacrifice results in his Logic card being torn up and scattered to pieces, but his Logic is eventually recovered by a spirit named Athena (pictured above), and he becomes a Logicalist once more.
A quick scan through the dub gives some more context:
[Athena holds out Tsurugi's Logic card] Athena: As long as you have this, you can fight.
Tsurugi: No, it couldn't be...
A: It is. Take it.
T: Why do you have my card?
A: I was looking for it. Now we can fight side by side.
Then there's a few more minutes of plot, and a transformation sequence wherein Athena and Tsurugi fuse, resulting in
Tsurugi with Athena's powers.