Well, the first thing I would do is maybe ask Yaya Han how he is as a person, while giving this story to her (only make it a little shorter). I mean, I would imagine she knows more about him than you do since she has worked with him. However, she is also busy so she might not get back to you quickly.
Second, I would try to continue and look for people who have also purchased from him. If this is a first time thing, I would honestly assume that he is extremely busy, or something personal has happened where he can't deal with business right now. It's important to understand that sometimes important family things come up.
However, I would keep sending him e-mails periodically. If he doesn't respond soon, I would go to your bank and see if they can do anything about it :\
-Mako (Kill la Kill)
-Popstar Ahri (League of Legends)
-Jill Valentine (Resident Evil 5)
-Poison (Final Fight)
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