I been reading the chainsaw man for 2 years now, and in my opinion Kakimoto did a better job than Fujimoto

The case of Asa is not exactly a split personality, but she and Yoru share the same brain. On the other hand, Mutsumi has a DID rather than just a split, but the director mentioned a split personality and at the time of the anime plot she really has a split personality. Because of all the roles only two are awake - Mutsumi and Mortis

In short, Asa and Yoru were a stereotypical duo. One is good, the other is bad. They are not afraid to lose control. Yoru have an excuse that she a demon and that's why she bad, but that doesn't change the case
Mutsumi and Mortis are different. They're not evil or bad, they're afraid of losing control and fighting for it all the time, and the symptoms look more like a real DID than a parody of it
Also in the manga it doesn't even matter anymore. Asa doesn't care if she dies, but she used to want her body back. And Yoru hasn't even changed. It' funny, but Mortis is really smarter than her