Since Rudeus doesn't seem to be able to say it, I'll say it for hom (VOLUME 16 WN SPOILERS)

Uhm...Seems like you didn't understand the story. Well, I'll elaborate it now.

First, didn't Future Rudeus himself adviced him not to try to oppose Hitogami? Rudeus was trying to do what his future self said. Rudeus can't do anything, can't touch Hitogami or harm him, that's why he needs to avoid opposing him. Remember that Hitogami is a trickster, he knows everything, every movement, every secret, every intention and action Rudeus is planning.

Second, saying out loud to others just mean dragging them into his mess, which Rudeus tried to avoid. Hitogami is a divine being, he would know, and if he knew, he would kill all of Rudeus' beloved ones before any of them could do anything. The obvious example would be when Rudeus went to meet Nanahoshi for advices, you knew what he had said to her "Please, Hitogami is watching". Yes, Hitogami was the mastermind behind this, he could do anything, even killing the whole Greyrat family if he saw Rudeus opposing him. Seriously, I think he could. After what had happened in the future, how we couldn't believe? Rudeus would never be able to realize when Hitogami did that until it was too late. He was nothing but a mouse in Hitogami's cage. It's like a stalker holding hostages with a gun in hand. No one can interfere with it. Only when Rudeus had Orsted's protection, he was able to escape from Hitogami's sight. He didn't know what's the truth, so he chose the best choice. Instead of going to fight against an enemy you have no chance of winning, misleading him to believe that you're his companions then turn the tide later seems to be a better choice.

Roxy and Sylphy had already noticed that there was something wrong with Rudeus. Even if Rudeus told them what had happened, what could they do then? Maybe they got killed off by Hitogami before knowing anything. Yeah I don't think plot armor could be activated in this case.

/r/mushokutensei Thread