It was pretty much confirmed that Fukube was friend. Even before this chapter. First of all his death was too suspicious, like if he wanted he could have shot "fake friend" on the bloody new years's eve. But just wasted time by saying all of that useless bullshit. And they never confirmed his death. But what really confirmed it for me was the virtual attraction thing. Where Sadakiyo's friend told him "I'll kill you, if u tell anyone about this". And later Sadakiyo, said that "friend" was always angry with him, and told him that he couldn't do anything without "friend". Also (kid)Fukube in the flashback and the kid who said he felt bad for collins in the flashback(flag on the moon ch), wore the exact same clothes. And fukube said that he invited Sadakiyo to the secret base, And from Sadakiyo's pov we see that the one who invited him(fukube) into the secret base is "friend". So this is a bit anti-climatic for me. Maybe Fukube is just a pawn. But I have no doubt that he is indeed Kanna's father.