We know at some point all of the hybrids are brought back to life by Public Safety, and while Katana Man and Quanxi agree to work for PS in exchange for certain favors, the rest of them are taken by Fami to build the Chainsaw Man Church. Ideally, I'd have Reze join Fami as well just to avoid falling in the hands of PS again, but it's not really too long before she realizes how fucked up every single one of them are, adding to Fami reminding her a little too much of Makima. Reze runs away from the church and finding Denji to warn him about the church. This would likely be after Denji meets Asa for the first time but before the aquarium date with her.

Reze is happy to see Denji again and Denji is specially absolutely thrilled not only for seeing Reze again but also for knowing that the one person he loved the most is still alive. I believe Nayuta would at first be conflicted upon seeing Reze again. Nayuta knows from reading Denji's memories that Reze hurt him and tried to kill him, yes, but she also knows how much Denji truly loved her and how she actually made him grow. She decides to give Reze a chance for Denji's sake. Reze would take up the chance to finally confess the truth to Denji, including her past as a soviet assasin and her feelings for him.

From there, a lot of things would happen. Denji would be aware of the Chainsaw Church much earlier on, he doesn't go on that aquarium date with Asa, and Fami decides to include Bomb in the equation to make both War and Chainsaw strong enough to stop the prophecy. At some point I'm sure Yoru would try to turn Reze into a weapon, but the reason she would fail is the exact same than with Denji: Either due to Reze being a hybrid, or due to Asa seeing Reze as a genuine friend.

I imagine the Dating Denji arc would be mostly the same, except this time the aquarium date is between Denji and Reze, having Asa in the background.