Overview
Exchange project (交流企画, kōryū kikaku) is a project on pixiv that focuses mainly on interaction.
This tag is used in conjunction with the project catalog tag.
Each participant creates an original character, submits a character sheet, and draws interactions between characters in illustrations.
All submitted characters are treated as "It is Okay to Draw", so there is basically no need to ask permission from the creator.
The term "exchange" in the exchange projects means "to let the characters interact with each other".