He just smirked
"Awww...~don't give me that darling-after all, you kissed back...~"
"Wellllllll-in case you haven't noticed, poor Lukas has been trapped here for some time...now-he's not getting out-you missed that chance Katsuki...he will never go with you...but....stay. Stay here, stay with him-and maybe you can start to rebuild that relationship again. maybe you can finally do right by him after all this time..."