Just an update for others:

Dear players,

We would like to inform everyone that we are aware of the problem with Fukurokumaru's Deals and Cave Exploration Rebate events. Due to error in system, both events ended sooner than they should. We plan to fix this issue during maintenance. Both events will come back once maintenance is over. All used ingots, coupons and cave keys will be added towards this event (since 01.10 23:59:59 till start of maintenance).

If you plan on spending your resources, we recommend to wait till this problem gets fixed.