One of the heroines in this game plays the role of a boke.

They do not need to be the boke in a real comedy duo. They just need to act like a boke in their everyday life. For example, their airheadedness may be a source of humor throughout the story.

Note, that a boke still needs a tsukkomi to interact with. If you don't have a tsukkomi, you probably want to use Airhead Heroine instead.

Similar in execution to the concepts of "funny man" and "straight man" in double act comedy, boke and tsukkomi are a very important characteristic of manzai (Japanese style of comedy). Boke comes from the verb bokeru which carries the meaning of "senility" or "air headed-ness" and is reflected in the boke's tendency for misinterpretation and forgetfulness. The word tsukkomi refers to the role the second comedian plays in "butting in" and correcting the boke's errors. In performances it is common for the tsukkomi to berate the boke and hit them on the head with a swift smack; one traditional manzai prop often used for this purpose is a pleated paper fan.

See Wikipedia and tvtropes for further reading.