Asking for ID in Japan (dating context)

[rosava45]

Hello

I've been watching a Japanese drama, and it has a scene in which a young man asks for an ID of a young woman he likes.
Could someone please explain what this ID stands for? It can't be a passport, right? Is this some social network's username or something?

Thanks in advance.

 

[Toritoribe]

Most likely that's Line ID.

Line (software) - Wikipedia

en.wikipedia.org

 

[rosava45]

Thank you!