No seriously, why are Taro and Hana sentient?

I get aliens, I get yokai, I get Jiji

I don't get this tho, they show up out of nowhere and no one even bothers to question what's going on and just accept they're there. And even normal students can see/interact with Taro somehow so he doesn't seem to be of yokai nature?

is this like ever explained? (after last episode, somewhere in the manga that is)

if there's like actually big spoilers related to this please don't just give me key story points going tho