Edison format ruling
Grave Ohja

Card effect (current official text)While there is a face-down Defense Position monster(s) on your side of the field, no player can select this card as an attack target. Each time a monster on your side of the field is Flip Summoned, inflict 300 damage to your opponent.
Rulings
- If you control "Grave Ohja" and you Flip Summon a Flip Effect Monster, the two effects go on a chain. You can choose which effect is chain link 1.
- If you control multiple copies of "Grave Ohja" and Flip Summon a monster, the effects go on a chain and you can choose the order of the chain links.
- The second effect of "Grave Ohja" is a Trigger Effect that activates when a monster is Flip Summoned. It can be chained to.
- If "Grave Ohja" is attacked, and you activate "Book of Moon" to flip another monster on your side of the field face-down, "Grave Ohja" has already been selected as the attack target so the attack proceeds as normal.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Edison forum — sourced change requests get reviewed.