SD23-JP001 SeaEmperor Dragon Poseidra
WATER/Sea-Serpent - Effect/7/2800/1600
Activate this effect by Releasing 3 Level 3 or lower WATER Monster you control. Special Summon this card from your hand or Graveyard. When this card is successfully Special Summoned by this effect, return all Magic and Trap Cards on the field to their respective owner's hands. If 3 or more cards are returned to the hand(s) by this effect, all Monster your opponent controls lose 300 ATK x the number of cards returned to the hand(s)
SD23-JP004 Armed Soldier of the Sea Empero
WATER/Sea-Serpent - Effect/2/0/1600
While this card is face-up on the field, once per turn during your Main Phase, you can Normal Summon 1 Level 4 or lower Sea-Serpent-Type Monster in addition to your Normal Summon or Set. (You can only gain this effect once per turn.). When this card is sent to the Graveyard for the activation of a WATER Monster's effect, select 1 face-up card your opponent controls and destroy it.
Hanzo search for ninjitsu, then use the trap card to eliminate an opponent monster and summon Sea emperor dragon Poseidra. When Poseidra is in your grave, you can summon Armed soldier of the sea emperor, summon diva on the same turn and summon another lv3 water via diva's eff. Then send everything to special summon Poseidra from the grave. Also Armed soldier will destroy a card on the field and Poseidra eff will let you retrieve ninjtsu to your hand to summon another poseidra.
It looks good to me.