You didn't write him out of character at all. And honestly, as someone with depression, I'd be more surprised if he wasn't depressed.

Oh my god... I got goosebumps and I still have them now. You are an incredible writer.

Kogoro's drinking and gambling us often portrayed in a light and humorous manner. Never thought there'd be a dark side to it...

The poor man. Good job looking at his character from another angle! It's not something very usual of Kogoro, but still quite possible!