Man, it really hurt reading this chapter... Ishidaira really wanted every chance to connect with his dad, but out of respect for his mother, he chose to avoid it. Then the bombshell possibility that they aren't even related, with his mother supposedly not knowing his actual father either. It makes it even worse when his mother has relationship with abusive and/or terrible men that require Ishidaira to step in and protect her, because it goes back to the question of what makes his dad so much worse than these men? Such a situation can really warp a child's view on adulthood and responsibility.
All in all, I do hope Ishidaira gets another chance of meeting with his dad. Probably even throught the book report itself. Since Ishidaira had always liked the author's work, and the author may have been his dad, it explains why Ishidaira is so fond of the books written by them, as they're the only ways he can keep up to date with his dad. All in all, it's a good thing that the biggest gift Ishidaira got from his dad, was his habit and joy of learning new things.
This is seriously a beautiful series.