WE cause cause kaz to have a mental collapse in his own dungeon to cause its destruction. As a result of this Ira will leave to preserve its own life as well as stealing the treasure for us, itself. This will not kill Ira as it is kaz's palace not Ira's. This will also leave kaz alone, we take him and leave, we dont need to fight that just increases chances of kaz dying, if kaz has a mental collapse Ira will think he is dead and wont bother killing him. When we leave we can bring kaz back, which will be very easy considering both jojo corpse party and neps are here as well as this being shown as possible by Shido. In short, no one gets hurt, Mishimanbs dosent have to see people die, shinji stops being a dick and we all live happily ever after, the end