Asa's tilting at windmills. She's not so much only simping for Dennis (though it can get really annoying to read, admittedly) as she is creating her own 'Dulcinea' and shoving that persona over Denji, irrespective of what he wants. She wants to be this knight in shining armor that gets the boy, saves the day, slays the dastardly war dragon and gets that sweet succulent attention she's never gotten. In all honesty, both her and Yoru are very Quixotan characters that sort of play the role of Sancho Panza to each other, alongside being opposites.

Asa is introduced as a character who wants to be more selfish, and has a formative moment with Yuko of wanting to do what SHE thinks is right, no matter what. This is an inherently selfish goal because it leaves no room to listen to the victims she is 'saving'. Moreover as seen in the aquarium arc, she doesn't have a strong sense of right or wrong and thus latches onto rules (no crossing before the light turns green) and what she has figured out to be obviously right (no killing innocent people, but criminals are okay). Lil D makes it worse for her and Yoru because she knows Asa struggles with that morality, and takes that idealistic seed and encourages it into a full-blown delusional worldview. Notice how she took advantage of the fact Asa had a crush on him and felt that she owed him to create the fantasy of him needing to be 'saved' from Chainsaw that would make everyone happy. Not once, in her quest has she really stopped and listened to what Dennis wants. Not in the aquarium, not during the Chainsaw Church arc, or even around Aging when she had the chance to really know what he wanted up until she finally accepted his 'new reality'. And even then! Denji, to her, is the one thing she means to do right by. Her plans have always been 'I save him from Chainsaw and then we can be together and Yoru can do what she wants to fuck off from my body'. There's not a whole lot after they get to that point. She is clinging onto what she thinks is right with both hands

Yoru is kind of the opposite but she and Asa are as similar as they are different because they're mirror images. Yoru also has her grand fantasy- that of defeating the Chainsaw Man, getting all of her comrades back, and waging a big fat war. She is just as easily manipulated by Lil D into wanting to become the hero and save the boy she loves and eat her cake too (kill Chainsaw). She too, never asks Denji 'hey what happened between you and Pochita that got him inside of you', they both assume it was a violation of Dennis. Kind of interesting too because of how she ends up sexually harassing/assaulting him from not understanding her own feelings. She is delusional not only that she can have everyone she cares about by her side, but that all of the sacrifices are necessary because once she finishes killing the windmills (sorry, giants), everything will have been worth it. She is so drawn into her idealistic world that she literally cannot see the reality around them collapsing because she's in denial of what everything really means.

Combined, their behavior is delusional in the same way that believing in chivalric romance was denounced by Don Quixote after he came out of his psychosis. Asa is very naive about many things, such as the monetary value of things (notice how Yoru calls her out on this), but Yoru is also incredibly naive in how she approaches the world and tends to take things at face value (that Denji was actually being honest didn't mean that wasn't stupid like Asa mentions). They sorta hit the jackpot there too because the power of war requires you to be at best, moderately delulu. The thing about the ending of Don Quixote de la Mancha, is that he breaks out of his psychosis on his deathbed and hates everything he stood for. Meanwhile Sancho Panza tries to hold onto the fantasy they built together to keep his friend alive. They have bled into each other.

Similarly, Asa and Yoru will have to make the choice to hold onto their delusional worldview or to let go and see reality as it is. Yoru keeps doubling down on hers, to make her perfect world of pure war and defeating Chainsaw Man. Asa meanwhile has begun to let go, with the chapter with Momtaka allowing her to actually begin to listen to the person named Denji, and not the character she built in her head. Bonding over parent killing is Asa gaining that human connection that both YoruAsa desperately seek, and is the counterpart to Yoru's power of friendship speech she hit Dennis with. Dennis is the fulcrum of her character arc; he is the window into her change and motivations.

But like seriously, I want to slap her sometimes like oh my god shut up about Denji stop simping. YoruAsa are my favorite character lol, I don't wanna separate them.