[Naruhodou kept himself out of Holmes' way to let him do his work, only saying something if spoken to. When the detective becomes fixated on a certain photo though and he sees what's on it, he breaks his silence.]

That...was taken on that same day. Professor Mikotoba and Judge Jigoku arrived in London to attend the Scientific Symposium. [It's probably going to hit him, that he had just missed seeing his partner.]