i don't think i thought about it, actually? maybe in these first few stories after 4piece their relationship will be more like trust-building and stuff, and if/when we eventually get focus events on the new kids they'll start exploring more about them lore-wise (if that makes sense)? i don't know if they'd hide that he's related to the sakumas though, since rei himself said he's happy to see more of their kind coming into the light and opening a path to others, making raika a known sakuma family member could be beneficial for their plan of having vampires/supernatural beings and humans living together under the sun, but idk.

you raised a good point, though, maybe having ritsu be a brother-like presence to raika could be good for him. at the same time i don't think that ritsu lacks understanding of rei, he does understand why he did what he did, he was just upset about it for a long time (especially as a child) and still acts petty around him bc, well, it's ritsu. but let's see how raika's addition to their little family circle affects their relationship.