The particle が can attach to a noun to identify it as the subject performing an action in a sentence.
Upon entering the café “Rabbit House” for the first time, Cocoa is astonished to find there are no rabbits.
ウサギ (“rabbit”) is the subject doing an action.
いない (“to not exist”) is the action being done.
Cocoa and Chiya first meet when Cocoa is savoring the look of the snack Chiya is offering to stray rabbits. After giving one to Cocoa, Chiya is please to hear Cocoa liked it, as Chiya make it herself.
Rize finds Cocoa really gets fired up when it comes to making bread.
ココア (“Cocoa”) is the subject doing the action.