Okay, New plan. Mom has to go away as the buff she provides to dad aka "I will never lose in front of my beloved" is too strong. Tomo should come in and give the double effect buff/debuff aka "Provide my beloved with power while glaring at dad so he gets nerfed" ... It's worth a shot against this demon.
Also, dad is being a right ass in demanding that Jun beat him to "date" his daughter. We get it ... you want to make sure Jun can protect her (not that she needs it LOL) and at the same time delay losing your precious daughter. But you are not losing a daughter ... you are gaining a son. A very relatively strong son.