I must say, I do love how the story so far keeps focusing on having an unbiased view of the crime is essential. Imma guess Mano's case was shut closed cause if it or something and it's not over yet.
Wait, so did he actually kill her and then himself? I thought forensics didn't find any DNA of the son
Yep. Which mean is the son killed her, she wasn't fighting back. Also They found the toppings of the sushi in the mom and the rice&nori in the son's stomach, which witnesses has said the son bought before the TOD. Which leads to the detective meeting the son's friend who told him about that recollection at the end. Basically, with the victim and perp dead, all they needed to find out was whether there was anyone else related to the crime which... there wasn't so case closed.