Tengu format ruling
Legendary Black Belt

Card effect (current official text)Equip only to "Chu-Ske the Mouse Fighter", "Monk Fighter", or "Master Monk". When the equipped monster destroys your opponent's monster by battle and sends it to the Graveyard, inflict damage to your opponent equal to the DEF of the destroyed monster.
Rulings
- "Legendary Black Belt" inflicts damage based on the original DEF of the destroyed monster (in the GY).
- If a monster equipped with "Legendary Black Belt" is destroyed, no damage is inflicted by the effect of "Legendary Black Belt" because it is no longer on the field. This includes if it attacked a monster with equal ATK, for example.
- After the monster is sent to the GY after being destroyed as a result of battle, the effect of "Legendary Black Belt" that inflicts effect damage can be chained to.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Tengu forum — sourced change requests get reviewed.