So he just calls out the lich right in the middle of everyone after telling Kana to be hush-hush about it? Unless it's something like Kana can only see it because she's his slave or something, because otherwise it seems like everyone should be freaking out just as much as Kana is.
It's still weird to me though how ingrained the slave behaviors are in Kana, even after she was mentally "cured" by the MC's food and she's hardly been a slave for long anyway, but still acts like she's been a slave all her life or something.