ok but none of that says if he doesnt get control then the effort was wasted and every attempt is like the first time, all that says is if he doesnt get control they could attack him, so unless theres been something said or to show the power wears off my suggestion could work. the only faults to it is if he doesnt get control his risks retaliation and finding opportunities to try it, then theres the questions of how much chakra do you have to infuse before she notices and how would she react.
kagura was kinda a 50/50 with how she reacted to things cause it seemed like one moment if someone tried something she would go right to 'how dare you you worthless incest' and tryin to kill them but then other times her reactions just like 'pathetic why do you even bother' and just ignoring them, so unfortunately or fortunately depending on how you look at it there seems to be too much that depends on the writers end to be able to know for sure how effective it would be but the reason i say its could be fortunate is that the game dev could go with the best case circumstances to make it happen if they really wanted to
Oh, no, it doesn't seem to wear off, but it won't start to affect the subject until a certain amount is given, which effectively means the same as not giving it. The problem isn't that it won't accumulate, it's that there needs to be enough accumulated on the very first attempt that she won't kill the MC as soon as he's done, which Tsunade would have done if even a little less had been poured into her, she definitely seemed to be right on that threshold. Example, the other four were put into a trance the first time because there was enough poured in to subdue them completely, but the same cannot be said of Tsunade. This threshold is different based on the subject's will, the strongest by will being Tsunade for the main girls and Anko for the side girls. Kaguya is most likely stronger willed than those two, so more chakra is required. This presents two distinct issues. There's the most basic issue in the Naruto universe, the amount of chakra one shinobi can have at any one time, which may or may not be enough to subdue Kaguya at least to the 'openly hostile, but unable to act on it' state that Tsunade was put into. There is also the strength of her will, which will determine how much of the MC's chakra stores have to be exhausted to pour that much into her and how much it will take for that state to be triggered. If either her will is too strong or the MC doesn't have the chakra reserves, game over. The MC won't get a chance to pour a second batch of chakra into Kaguya unless he can pour enough in to get her over that threshold because that threshold will determine if the MC will be able to live long enough to take a second shot. As far as her noticing the chakra, she wouldn't as long as enough is poured into her that she is completely subdued into a trance state like the first four main girls. She would, however, notice once the MC snaps her out of the trance, like the first four girls did, or if only enough chakra was used to keep her from killing the MC, like Tsunade.