The "When this card is sent to the Graveyard by your opponent's card effect" effect activates in the Graveyard and it starts a Chain Link. (This is a mandatory effect. It will activate even during the Damage Step or if this card is sent to the Graveyard by an effect activated as Chain Link 2 or higher.)
This effect won't activate if this card is not in its owner's possession when it's sent to the Graveyard by an opponent's card effect.
This effect will activate not just if this card is sent from the field to the Graveyard, but also if it's sent from the hand or Deck to the Graveyard by an opponent's effect.