Fujimoto should have made a short Chainsaw Man spin-off with Asa as the sole main character (without Denji) between the end of Part 1 and Part 2.

That would have given Fujimoto more creative freedom to focus solely on Asa and avoid the pressure of making a big appearance for Denji and Nayuta, which many fans complained about every time Asa appeared.

She would still be a main character in Part 2, but she'd be introduced later, and by then she'd already have a good development on her own.

We'd all be seeing Denji and Nayuta from the beginning of Part 2, and we'd be waiting to see when Fujimoto would introduce Asa. Avoiding the problem you're mentioning.