I managed to get the Team Sirius events without using the support card (through random events). I wonder if this is possible with other support cards like Riko Kashimoto or Tazuna.
I think I should use it on Super Creek or Biko Pegasus, or even Matikanefukukitaru, but whenever I ask someone about it, they tell me it's not worth using it on Super Creek because she is at 0lb, that Biko Pegasus isn't a very good card to use vouchers on, and that Matikanefukukitaru won't be very useful after Trackblazer. So what the heck should I do? I guess these vouchers will just stay in my inventory forever and I won't have any utility for them