Keiji is getting married and wants his father there. The problem is... he has never known who his father is. After finding his dad's old diary he realizes that there are three possible candidates. So he invites all three of them to his wedding. What could go wrong? (A Haikyuu x Mamma Mia AU. The plot will be based on the movie, with my own touches sprinkled into it. I got very inspired from a work on AO3, "The Winner Takes it All" by runningfromrealitytoanime) ! I don't own any of the characters or anything you might recognize from the anime or movie !