Ah yes, the magical taser that when it grazes your hand it knocks you out cold and wipes your memories. Truly a pinnacle of modern self defense engineering.
Feels like the manga has run out of ideas. It used to be about pretty funny misunderstandings, and now it's about a basic, contrived romance. This whole "antihero protects love interest through violence" cliche is an awfully dark turn, as you said, and it's the last straw for me.