Responses
To me the last chat with the ex-detective seems to me actually taking place in the family restaurant, and MC is just like "thinking" about it, or something. It's for the manga to sort of give the answer to that last question ㅡ "where are you going after this, don't you want to stay with me" ㅡ and the answer is going to the sea (commit suicide). Or at least that's how I interpret it.
Honestly good ending but like... what exactly happened in the end there lol. Like did he suicide with the guy watching? Or was that just the last chat he had before going down near the water? Probably that.
Anyway, may they meet eachother in a more happier family background.