Rita would stop outputting Futon by this point, satisfied with the growth of the storm. However, she could senses the great build-up and release of chakra that would accompany the mass shinrai tensei. While she could defend herself from the attack, she had expended a decent amount of chakra already.
She would poof, and return to her residence for the time being.
No, what was needed was a slight change in action. Due to the orientation of the sun, the storm, and of course his foe's position, then while the Shinrai would successfully be able to divert thingss in its path, it still overlooked the actual tool of which Eric intended on using.
It was not the storm itself that was Eric's attack. It was the shadow. And from that shadow, from the shadow of the massive storm, came the hundreds of kunai and shuriken. They were not released until the moment the attack began to reach them. This timing could be done in part because as the debris of the tower would be diverted from its structure and outwards (from top to bottom), it would stretch out a shadow, eventually, at just the right moment, leading up to the entrenched knives that Eric had remote manipulation of.
So, it would be in this moment that the hundreds of kunai would leave the shadow, directed and controlled by Eric's chakra. They were then maneuvered, in this short window, to detonate in a manner that would allow the explosions, both poison and explosion, to completely surround Ichirou. Since this was within the gravity space of the Shinrai tensei, it would not be blown away, and since Ichirou was both in the air and likely having to briefly recover from his usage of such a powerful technique, it would be incredibly difficult for him to completely dodge the attack.
The poison cloud, Mushū no Dokugiri; Odourless Poison Mist would be odorless , but it would be seeable as a purple cloud. Of course, in the mix of regular smoke and the such, it would be difficult to pick apart in the thick of it. Upon inhalation, the mist would dramatically reduce the reaction time of those who inhale it; if Ichirou were to take the full dose and stay within this foul cloud for 2 turn, it would outright kill him, though being in it for just one turn would merely hamper his reaction time to the point in which it would take much longer for each of his senses to register the world around them. This was courtesy to the Greenhouse Keeper of Sunagakure during Eric's rather brief tutelage in poison.
Of course, though he had unleashed his attack, Eric was still at the walls; and he still needed to worry about being completely blown away. Due to the time spent coordinating his attack in the midst of the gravity, all Eric would have time to do would be to utilize his tailed beast for the first time ever, bringing upon him a cloak of red chakra. While it would not perfectly shield him from the attack, it would keep the initial impact, and the subsequent physics, from outright killing him, knocking him unconscious, or otherwise impaling him with debris.