Apologies for delay.
--
Seeing Luffy begin his attack, Chun remains cool, and as Luffy's kick is about to hit him Chun ducks, the momentum from the kick should lead Luffy rotating. Other than that, Chun would, after ducking and after the kick passes above him, raise his head while taking a step forwards. He would simultaneously raise his right hand and strike in between Luffy's leg, this attack should lead to Luffy's gentles getting damaged, furthermore, Chun would use his other hand, the left one, and grab onto Luffy's back shirt. He would, with the usage of both hand and his upper body, attempt to throw Luffy towards the ground in front/beneath of him. After that he would take a step forwards, placing himself slightly behind Luffy's head. He could see the body of Luffy through his peripheral vision in this position.
Last chance.