Tbh solving this situation would've been hella easy.
1. Hint at this possibility earlier. Have the Lawyer fight someone and steal the CT of a weapon that he used for a bit but that isn't very significant. The best option would be a fight against someone and have Higuruma use confiscation right before the fight ends because of some interference. Then we could see a small dialogue where the character whose weapon got confiscated says something like "This doesn't work anymore, useless" and then throw the Cursed Tool away and boom, some discreet foreshadow for this bs.
2. Give Sukuna his dagger a little bit earlier and let him murder quite a lot of people in Shibuya with a huge AOE attack. If you want to keep this a secret just draw the panel from a further perspective with Sukuna throwing lightning for some unknown reason.
This would solve it quite beautifully imo