Help! 30-day landing visa

My American boyfriend is coming to Taiwan on 21. I’ve already booked him a one-way ticket. Just now I realize he needs either a tourist visa or a return ticket to enter Taiwan. Does it mean he won’t be able to get a landing visa at the airport? Our original plan is that he stays in Taiwan for a couple of week, then get a flight here and leave for Korea. He has a Korea working visa (E2) on his passport. Can it, instead of a outbound ticket, help to get the landing visa? Or I should book a ticket (Taipei to Seoul) for him in advance? But even if we do this, how can the immigration office know my boyfriend has got a flight out since the ticket will be in my hand, not his? Any help will be appreciated.

I had a similar problem, without the boyfriend part becasue I’m a guy. When I was checking in at the airport they said that I would not be able to go because I had only a one-way ticket and a visitors visa. So I quickly had to purchase a return flight. Then when in Taiwan I went to Air Canada and canceled the return ticket and got my money back, not all but most.