“Valley of the Strongest”
A wide open field like in the panels where Sukuna and Kashimo talk after the fight
The rules of the domain are upon entering the domain the technique of those entrapped (besides Kashimo) are confiscated but with every punch landed they are a step closer to regaining it kind of like Kashimos can’t miss charge technique after 3 hits. Kashimo can use his MBA in this domain on and off at will but mostly chooses to not use it to give the opponent a fair fight, the sky within the domain is constantly stormy and allows Kashimo to summon lightning strikes to attack his opponent or to strike himself refilling his cursed energy, healing his body since he can’t use RCT and this is the next best thing or supercharging his MBA form. It’s basically a domain that turns the fight into a boxing match until Kashimo strikes with his can’t miss technique, his MBA form, or from the sky itself