Donghae has always been a sensitive person- simple words tend to leave a scar deeper than any can imagine. None were enough to kill him, but overtime their accumulation bled him of the humanity him had once had. Masking his devastation behind a laugh, he never shows how much harsh words could cut through him. So when Eunhyuk labels their friendship as 'colleagues and nothing more', Donghae might have just died a little on the inside.