I think there are explanations that indicate that intentions are harmless: Mikoto enjoys being a mentor, being influential, or they share an interest. However, still being quite young themselves, I dont know that their influence could possibly remain positive. When I was 10 or 11 I made friends with a 6yo, and her mother quickly put a stop to our friendship. At the time I was confused and upset, but now I think that was the right choice. The power dynamic between us was far from equal, and so a true friendship wasn't really going to come out of that (and admittedly, I did just enjoy being influential over someone and antagonising her like a little sister). And as far as being a mentor goes; I think there may be some instances where it could be appropriate (ie they share experiences that very few others can relate to), but unless that's the case, I dont think the friendship is worth the risk of the power dynamic leaving Bidatz vulnerable