@vannn Miko is a size queen, all she needs to dump her boyfriend is a big dick and Sasu has a big dick, is a classic NTR story, she gets mind broke by a big cock.
And Saku is a cuck all he needs is for Amane to join a swingers circle which they are already making, and cuck him with different strangers, not just with the guys she selects.
Miko can't satisfy this because she has standards, like i said she is a thot but she is a thot with standards, she will only go for big dicks and this is probably the first time Saku is going to live his cuck fantasy.
Amane on the other hand can become Saku's dream thot and cheat on him with lots of men while he watches, without the requirement of all of them having to be a certain size, she can become a woman that cucks him not to please herself like Miko does, but to please Saku which is what Saku wants.
Miko and Saku's relationship is not really stable at all, for starters it seems they got together just for appearance's sake, to be the power couple, but they are sexually frustrated, their fetishes are perfect for their relationship to crumble extremely fast the moment someone that can satisfy their fantasies comes.