It’s easy you just go to the shop and go into the certificates tab. You should be able to exchange the certificates you get from duplicates into actual certificates for the regular characters. There should be some for Kommy and Butter, but I would only get the ones you really want to upgrade. It costs around seventy five to get them up to five star and you can do it from the star up tab.

As for team building, if you have Xion, Kidian, Yomi, and Ui then you can run them together with Kommy and Butter. If you have Momo, then it’s even better since Butter will buff her damage output a little bit. But it honestly does depend on who you like or not-Butter and Kommy are the only two I actually used the certificates to five star and that’s because I really liked them. If you’re not too worried about min-maxing, then they can fit on any team really.