Dāto took note of the Yondaime taking advantage of his previous attack. He frowned slightly from his position in the air as the fog would begin to take on a very weak purple hue. “You aim to make your poison airborne then, huh?” He asked himself quietly. If he didn't act carefully, the Mist Denizen might find himself in quite the predicament. Seeing as how the western half and the ocean outside of the Kirisame blanket were swiftly becoming under Trev's control, Dāto didn't have the advantage to launch his prepared move. He also knew that by diffusing the poison into an ever in motion body of water, especially with splashback and current undertow caused from the rain, the Dokuton would have to be rather diluted. Coupling this fact with introducing it to the superheated fog would weaken it further. Still, Dāto didn't know what type of poison it would be to counter with the antidotes he has with him nor what effects it would take on his body. He wasn't going to risk exposure.
He flew up higher, even though the increasing poisoned-infused fog would take some time to even threaten him immediately, so he could act near the lower lying clouds. This next move would require more contact and concentration than his first move. He formed the Horse handseal and closed his eyes. His five tails would wave in the air before chakra was pulled from them and infiltrated the clouds causing them to become fully saturated with his signature. The moisture could not be contained as it fell to the ground. Trev might believe it to be Kirisame once more to try and give the Terumī back advantage. But he would most certainly be wrong in assuming so.
As the rain fell from the sky and made contact with any foreign entity, be it even as small as a droplet of vapor, a faint hissing sound would emit to denote that it would be dissolved instantly by the highly concentrated acid. This rain was no laughing matter and shouldn't be taken lightly. The only items not affected by the rain would be the ones attached to the Terumī, the Terumī himself, and techniques that contained his chakra. It fell to the increased water level on the western half of the island and through the fog, dissolving everything it touched along the way. Even the Dokuton on the surface of the water would dissolve away as the Mist denizen's acidic rain fell. It fell in a much more heavy torrent than the rain on the eastern half of the island. Its initial circular spread would begin with an astonishing 1000 yard stretch, easily overlapping into the Kirisame on the eastern half of the island. This would ensure that Trev and his ethereal warrior would not be able to easily flee before the Susanoo was completely dissolved despite its Sage enhancement. Also, the marked kunai would just so happen to be within the spread and therefore it too would face dissolution, especially the seal. Due to the large size of this technique, his shroud would lose three tails leaving him with a two tail shroud.
(Futton: Sansei Ame no Jutsu; Boil Release: Acid Rain Technique)
Trev could, theoretically, maintain the Susanoo though he would find he'd have to focus most if not all his chakra and attention into maintaining its large form due to the constant barrage that was beset upon him. Assuming this would be the case and that his new rain would dissolve the already weakened Dokuton, Dāto would fly just a bit down from the clouds in order to observe his handiwork. He held a single kata, waiting for his opponent's next move.
ONLY IF the Susanoo shows any opening in its defense, then a jikūkan would erupt rapidly in the opening and two of his clones would pop out. An untransformed (V1, one-tail shroud) clone would be carrying a transformed (V2, three tail shroud) clone which would let loose its bijūdama point blank at Trev. It would carry enough strength to blast through his Sage enhanced form to cause some serious, if not fatal, damage that would prevent his Edo Tensei body from reforming immediately and allowing the Mist denizen time to seal up his remains. Both clones would be sacrificed in the explosion, granting the Mist denizen back his chakra.
IF NO OPENING OPENS, then nothing else happens.