I’m really sorry you have to deal with that. But unfortunately not even EC can prevent resellers from ripping off the textures of your cards.
Like our visitor
@user293 did here
kemono.cr
But you must keep your head cold, the hard truth is that sharing/selling on Koikatsu involves the risk that someone might sell/leak it. The koi community grew in size, even sellers are now dealing with resellers, and also feeling a lot pain from it. Because all koikatsu users, minus the steam ones, are pirates, we are all not trustworthy and uptight by default, even you broke that trader trust when you shared that Suou card, even if he wasn´t a uptight guy himself. So if it bothers you, the only real way to stop these bad guys is simply don´t distributing it at all in the first place, accept or leave, like Panecito and lot of others did.
I know you´re taleted Anni93, I like your Maple Colors cards, even thought I see some of the accessories incorrect on my end, I can see you put a lot of effort into the outfit overlay, outfit accessories and especially the hair. There's not much competition because of how forgotten Maple Colors is nowadays, but I'm really glad you showed it some love, and did so with a lot of affection, and I´m really glad you shared it. If I want your full cards, I guess I will just need to download EC and screenshot the accessory tab myself, but still so much better than starting from nothing, so thank you.