Tachibana Kanade (aka Angel) is a prominent figure in Angel Beats. The SSS,
at least in the first few episodes,
is constantly fighting her, but she has certain abilities that make her very difficult to defeat.
However, it's revealed that abilities aren't
God-given, instead, she uses software called Angel Player to create these abilities herself.
Angel Player was created by the Programmer, as stated in Episode 11. The Programmer is an elusive figure, who likely didn't even know Kanade.
So how did Angel Player find its way to Kanade, for her to later use?