It's a kiss from when Sonata is mourning her lost powers and Sunset wants to comfort her and be there for her (and maybe a lot more comforting more later).Don't worry, having disturbing thoughts are a pretty normal, human thing (I think we just like to pretend we don't have them but it's okay). Your violent interpretation makes me wonder if your own inner narrator can't trust things to be entirely genuinely sweet without a dark side or you favor imminent tragedy paired with your romance. Either way glad you like my art, read it as you like and Clop on friend!