Bunkasai means "cultural festival" - you often see it in teh animez set in school. All the classes work on producing some kind of fun/creative feature (e.g. food stands, themed cafes, haunted houses, sports/games, drama/music performances, etc.), and then the school is opened up to the public to see it all

On Heyuri, we designate a specific day (though things like this are fully welcome any day of the year) for us to all create fun/creative things for each other to see and experience

There's no limits or expectations - just whatever you (or your group) can come up with