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".