When your “Hino-Kagu-Tsuchi” inflicts Battle Damage to your opponent, he / she discards his / her hand before drawing in their next Draw Phase. If their next Draw Phase is skipped, they discard at the start of the Standby Phase. If the Draw Phase and Standby Phase are skipped, they discard at the start of Main Phase 1.
The opponent cannot activate any effects at the start of their turn before they discard their hand for the effect of “Hino-Kagu-Tsuchi”.
Netrep Rulings:
There are no chainable events before you Draw a card (and “Hino Kagu-Tsuchi” does not need to be errata’d). You cannot activate anything prior to Drawing a card. “Hino Kagu-Tsuchi” is not activating prior to the Draw. It is resolving. In any case, the effect of “Hino Kagu-Tsuchi” will resolve but, quite frankly, doesn’t even care if it is at the beginning of your Draw Phase. If your Draw Phase is skipped it will happen at the beginning of your Standby Phase. If your Draw Phase and your Standby Phase are skipped, it will happen at the beginning of your Main Phase 1. And so on and so forth.
If “Skill Drain” is active when “Hino-Kagu-Tsuchi” inflicts Battle Damage, “HinoKagu-Tsuchi’s” discarding effect will not activate. If “Skill Drain” is activated after “Hino-Kagu-Tsuchi” inflicts Battle Damage, “Hino-Kagu-Tsuchi’s” discarding effect will still activate.