We are seeing a whole new dimension of our Main characters now.
I don't know if Hideo truly didn't care about Oda. I don't want to believe it but it may be possible. After all, he admitted that he cut the head off his former girlfriend because she mentioned her Ex. And yet, despite what his imaginary friend says, I don't think Hideo is unaffected. He went under the sheets when he was reminded of Oda's piss pants. I think he's in shock, and is coping by talking to the imaginary friend.
Hiromi though... She's clearly upset but I can't tell if it's about Oda, or about her freakin armpits... Or maybe they are both just coping. I mean, her aggression and insults towards Hideo could be a way of avoiding the reality of Oda's death.