Individual Card FAQs:
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.