Option to change their skins or revert to their previous looks is not possible since it is about the copyright of the designs .. That's what Daiske said in Official Discord Channel ..

Then that's your fault for buying her frags .. I was once tempted to buy her when she was available in Konoha Great Tree before but my only reason why i want her because of her appearance and for transformation use only .. With that motive, and the weight of things i considered, getting her frags for free is the best way and spending coupons on much better and important things is more way better specially that i am a F2P player ..

Getting what you've spent because they changed the appearance is not possible .. It is like you've bought a gum and chewed it and you wanna return it because you didn't want the flavor .. Once you purchased something in this game and if the reason is not that super viable or not heavy, then do not expect for refunds .. Specially if you spent coupons only and not ingots ..